```html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">

<title>Minimal Pairs – "ten" and "den" – Listening Discrimination</title>

<meta name="description" content="Listening discrimination practice contrasting /t/ and /d/ in British English.">
<meta name="keywords" content="British English,pronunciation,phonology,phonemes,minimal pairs,listening discrimination,language learning,teaching,efl,esl,elt">

<style>
@page {
    size: A4;
    margin: 20mm;
}

* {
    box-sizing: border-box;
}

html, body {
    margin: 0;
    padding: 0;
}

body {
    background: #e5e5e5;
    color: #222;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 17px;
    line-height: 1.6;
}

.page {
    width: 210mm;
    min-height: 297mm;
    margin: 15mm auto;
    padding: 20mm 25mm;
    background: white;
    box-shadow: 0 0 10px rgba(0,0,0,.22);
}

.screen-nav {
    margin: 0 0 20px;
    padding: 8px 0;
    text-align: center;
    font-size: 14px;
    border-bottom: 1px solid #ddd;
}

.screen-nav a {
    color: #245a8d;
    text-decoration: none;
    margin: 0 6px;
}

.screen-nav a:hover,
.screen-nav a:focus {
    text-decoration: underline;
}

h1 {
    margin: 0 0 24px;
    text-align: center;
    font-size: 21px;
    line-height: 1.3;
    font-weight: 600;
}

.introduction {
    margin: 0 auto 24px;
    text-align: center;
}

.phoneme {
    font-family: "Lucida Sans Unicode", "Arial Unicode MS", Arial, sans-serif;
}

.instructions {
    max-width: 650px;
    margin: 0 auto 28px;
    text-align: center;
}

.example {
    margin: 0 auto 30px;
    padding: 12px 18px;
    max-width: 600px;
    text-align: center;
    background: #f5f7f9;
    border: 1px solid #ddd;
}

.question-area {
    max-width: 650px;
    margin: 0 auto;
    text-align: center;
}

.question-number {
    margin-bottom: 12px;
    font-size: 16px;
    font-weight: bold;
}

.listen-button {
    display: block;
    margin: 0 auto 28px;
    padding: 12px 28px;
    min-width: 130px;
    border: 1px solid #245a8d;
    border-radius: 4px;
    background: #245a8d;
    color: white;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 17px;
    cursor: pointer;
}

.listen-button:hover,
.listen-button:focus {
    background: #1d496f;
}

.answer-buttons {
    display: flex;
    justify-content: center;
    gap: 35px;
    margin: 0 auto 24px;
}

.answer-button {
    min-width: 150px;
    padding: 13px 20px;
    border: 1px solid #888;
    border-radius: 4px;
    background: white;
    color: #222;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 19px;
    cursor: pointer;
}

.answer-button:hover,
.answer-button:focus {
    background: #f0f0f0;
}

.answer-button:disabled {
    cursor: default;
    opacity: 1;
}

.feedback {
    min-height: 54px;
    margin: 15px auto;
    font-size: 18px;
    font-weight: bold;
}

.next-button,
.restart-button {
    padding: 9px 20px;
    border: 1px solid #555;
    border-radius: 4px;
    background: #eee;
    color: #222;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 15px;
    cursor: pointer;
}

.next-button:hover,
.next-button:focus,
.restart-button:hover,
.restart-button:focus {
    background: #ddd;
}

.score {
    margin-top: 28px;
    font-size: 17px;
    font-weight: bold;
}

.final-message {
    margin: 20px auto;
    max-width: 600px;
    text-align: center;
    font-size: 19px;
}
.footer {
    margin-top: 24px;
    text-align: center;
    font-size: 13px;
}

.hidden {
    display: none !important;
}

@media (max-width: 800px) {

    body {
        background: white;
    }

    .page {
        width: 94%;
        min-height: auto;
        margin: 20px auto;
        padding: 24px 28px;
        box-shadow: none;
    }

    .answer-buttons {
        gap: 15px;
    }

    .answer-button {
        min-width: 120px;
    }
}

@media (max-width: 500px) {

    .answer-buttons {
        flex-direction: column;
        align-items: center;
        gap: 12px;
    }

    .answer-button {
        width: 80%;
    }
}

@media print {

    body {
        background: white;
        font-size: 12pt;
    }

    .page {
        width: 100%;
        min-height: 0;
        margin: 0;
        padding: 0;
        box-shadow: none;
    }

    .screen-nav,
    .listen-button,
    .next-button,
    .restart-button,
h1 {
        font-size: 18pt;
    }

    .footer {
        font-size: 9pt;
    }
}

.next-exercise {
    margin: 28px auto 0;
    padding-top: 18px;
    border-top: 1px solid #ddd;
    text-align: center;
    font-size: 15px;
}

.next-exercise a {
    color: #245a8d;
    text-decoration: none;
}

.next-exercise a:hover,
.next-exercise a:focus {
    text-decoration: underline;
}

@media print {
    .next-exercise {
        display: none;
    }
}
</style>
</head>

<body>

<div class="page">

    <div class="screen-nav">
    <a href="minimal-exercises.html">Minimal Pairs: Listening exercises</a> |<a href="minimal.html">Minimal Pairs</a> |
        <a href="phono.html">L1 pronunciation problems</a> |
        <a href="index.html">Home</a>
    </div>

    <h1>
        Minimal Pairs –
        <span class="phoneme">/t/</span> and
        <span class="phoneme">/d/</span>
    </h1>

    <p class="introduction">
        <span class="phoneme">/t/</span> as in <strong>"ten"</strong>
        &nbsp; · &nbsp;
        <span class="phoneme">/d/</span> as in <strong>"den"</strong>
    </p>

    <p class="instructions">
        Listen to the word and choose the word you hear.
    </p>

    <div class="example">
        <strong>Example:</strong><br>
        Press <strong>Listen</strong>. You will hear one of the two words.
        Choose the word you hear.
    </div>

    <div class="question-area">

        <div id="quiz">

            <div class="question-number" id="questionNumber">
                Question 1 of 21
            </div>

            <!-- There is deliberately only ONE listening button. -->
            <button
                type="button"
                class="listen-button"
                id="listenButton">
                🔊 Listen
            </button>

            <div class="answer-buttons">

                <button
                    type="button"
                    class="answer-button"
                    id="answerA">
                    ten
                </button>

                <button
                    type="button"
                    class="answer-button"
                    id="answerB">
                    den
                </button>

            </div>

            <div
                class="feedback"
                id="feedback"
                aria-live="polite">
            </div>

            <button
                type="button"
                class="next-button hidden"
                id="nextButton">
                Next question
            </button>

            <div class="score" id="score">
                Score: 0 / 21
            </div>

        </div>

        <div id="finalScreen" class="hidden">

            <div class="final-message" id="finalMessage"></div>

            <button
                type="button"
                class="restart-button"
                id="restartButton">
                Start again
            </button>

        </div>

    </div>

    <p class="instruction">
        Listen carefully to the difference between the two consonant sounds.
    </p>

    <div class="footer">
        Listening discrimination practice – British English consonant contrast
    </div>
<div class="next-exercise">
    <a href="minimal2526i.html">
        Next exercise: Minimal Pairs – &quot;coal&quot; and &quot;goal&quot; – Listening Discrimination →
    </a>
</div>

</div>

<script>

/*
    MINIMAL PAIRS – /t/ AND /d/

    Each item contains the two words from the source exercise.
    The order of the questions is randomised.
    Within each question, either word may be selected as the
    word to be heard.
*/

const pairs = [
    ["ten", "den"],
    ["tip", "dip"],
    ["town", "down"],
    ["team", "deem"],
    ["tier", "dear"],
    ["try", "dry"],
    ["trip", "drip"],
    ["true", "drew"],
    ["latter", "ladder"],
    ["bitter", "bidder"],
    ["whiter", "wider"],
    ["hearty", "hardy"],
    ["catty", "caddy"],
    ["Pattie", "Paddy"],
    ["cites", "sides"],
    ["putting", "pudding"],
    ["paint", "pained"],
    ["state", "stayed"],
    ["set", "said"],
    ["bent", "bend"],
    ["Crete", "creed"]
];

let questions = [];
let currentQuestion = 0;
let score = 0;
let answered = false;


/* Shuffle an array without changing the original. */
function shuffle(array) {
    const copy = array.slice();

    for (let i = copy.length - 1; i > 0; i--) {
        const j = Math.floor(Math.random() * (i + 1));
        [copy[i], copy[j]] = [copy[j], copy[i]];
    }

    return copy;
}


/*
    Create the questions.

    The pair order is randomised, and the word to be heard
    is also randomised for every question.
*/
function createQuestions() {

    questions = shuffle(pairs).map(function(pair) {

        const heardIndex = Math.random() < 0.5 ? 0 : 1;

        return {
            first: pair[0],
            second: pair[1],
            heard: pair[heardIndex]
        };

    });
}


/*
    Speak the selected word.

    speechSynthesis is used rather than an external audio file,
    so the exercise does not depend on missing MP3 files.
*/
function speakWord() {

    if (!("speechSynthesis" in window)) {
        document.getElementById("feedback").textContent =
            "Speech synthesis is not available in this browser.";
        return;
    }

    window.speechSynthesis.cancel();

    const utterance = new SpeechSynthesisUtterance(
        questions[currentQuestion].heard
    );

    utterance.lang = "en-GB";
    utterance.rate = 0.82;
    utterance.pitch = 1;
    utterance.volume = 1;

    window.speechSynthesis.speak(utterance);
}


/* Display the current question. */
function showQuestion() {

    answered = false;

    const question = questions[currentQuestion];

    document.getElementById("questionNumber").textContent =
        "Question " + (currentQuestion + 1) + " of " + questions.length;

    /*
        The two visible answer buttons contain the actual words.
        They are never blank.
    */
    document.getElementById("answerA").textContent = question.first;
    document.getElementById("answerB").textContent = question.second;

    document.getElementById("answerA").disabled = false;
    document.getElementById("answerB").disabled = false;

    document.getElementById("feedback").textContent = "";

    document.getElementById("nextButton").classList.add("hidden");

    document.getElementById("score").textContent =
        "Score: " + score + " / " + questions.length;

    /*
        Speak automatically when a new question appears.
        The learner can press Listen again if necessary.
    */
    setTimeout(function() {
        speakWord();
    }, 250);
}


/* Check the learner's answer. */
function checkAnswer(selectedWord, button) {

    if (answered) {
        return;
    }

    answered = true;

    const correctWord = questions[currentQuestion].heard;

    document.getElementById("answerA").disabled = true;
    document.getElementById("answerB").disabled = true;

    if (selectedWord === correctWord) {

        score++;

        document.getElementById("feedback").textContent =
            "✓ Correct. You heard \"" + correctWord + "\".";

    } else {

        document.getElementById("feedback").textContent =
            "✗ Incorrect. The word was \"" + correctWord + "\".";
    }

    document.getElementById("score").textContent =
        "Score: " + score + " / " + questions.length;

    if (currentQuestion < questions.length - 1) {

        document.getElementById("nextButton").classList.remove("hidden");

    } else {

        showFinalScore();
    }
}


/* Move to the next question. */
function nextQuestion() {

    currentQuestion++;

    if (currentQuestion < questions.length) {
        showQuestion();
    }
}


/* Show the final result. */
function showFinalScore() {

    document.getElementById("quiz").classList.add("hidden");

    const finalScreen = document.getElementById("finalScreen");

    finalScreen.classList.remove("hidden");

    document.getElementById("finalMessage").innerHTML =
        "<strong>You have completed the exercise.</strong><br><br>" +
        "Your score is <strong>" +
        score +
        " / " +
        questions.length +
        "</strong>.";
}


/* Restart the exercise. */
function restartExercise() {

    window.speechSynthesis.cancel();

    currentQuestion = 0;
    score = 0;

    createQuestions();

    document.getElementById("quiz").classList.remove("hidden");
    document.getElementById("finalScreen").classList.add("hidden");

    showQuestion();
}


/* Button events. */

document.getElementById("listenButton").addEventListener(
    "click",
    speakWord
);

document.getElementById("answerA").addEventListener(
    "click",
    function() {
        checkAnswer(
            document.getElementById("answerA").textContent,
            this
        );
    }
);

document.getElementById("answerB").addEventListener(
    "click",
    function() {
        checkAnswer(
            document.getElementById("answerB").textContent,
            this
        );
    }
);

document.getElementById("nextButton").addEventListener(
    "click",
    nextQuestion
);

document.getElementById("restartButton").addEventListener(
    "click",
    restartExercise
);


/* Start the exercise. */
createQuestions();
showQuestion();

</script>

</body>
</html>
```