Concept:The required vowel sound is the long open-mid back vowel /ɔː/.
Explanation:Among the given words, only "born" is pronounced /bɔːn/, which contains the exact vowel sound /ɔː/.
"cough" is pronounced /kɒf/, with a different short vowel.
"boat" is pronounced /bəʊt/, with a diphthong.
"done" is pronounced /dʌn/, with a short /ʌ/ vowel.
Therefore, the correct match is "born."
Answer:B. born