Concept:Identify the word whose underlined vowel sound matches the vowel sound in "open".
Explanation:The underlined "o" in "open" is pronounced as the diphthong /əʊ/, like in the word "go".
Option D, "phone", is pronounced /fəʊn/.
This contains the same vowel sound /əʊ/ as "open".
Option A, "chaos", has /eɪ/ sound.
Option B, "coin", has /ɔɪ/ sound.
Option C, "boar", has /ɔː/ sound.
So only "phone" matches the vowel sound of "open".
Answer:D. phone