/ɔ:/ as in "four" · /ɜ:/ as in "fur"
Listen to each word and decide which vowel sound you hear.
Choose FOUR if you hear /ɔ:/, or FUR if you hear /ɜ:/.
You can listen to the word again before answering.
/ɔ:/ is the vowel sound in four, court, form, short.
/ɜ:/ is the vowel sound in fur, curt, firm, shirt.
Concentrate on the vowel sound itself rather than on the spelling.