Concept:The symbol /ɔɪ/ is a diphthong sound, a glide from one vowel position to another. In English, it is commonly written as "oi" or "oy".
Explanation:The word "coin" is pronounced as /kɔɪn/. It clearly contains the target sound /ɔɪ/ between the /k/ and the /n/.
"Note" has the vowel sound /oʊ/, not /ɔɪ/.
"Stock" has the short vowel sound /ɒ/, not /ɔɪ/.
"Roam" also has the vowel sound /oʊ/, like "note".
Therefore, among the given options, only "coin" matches the phonetic symbol /ɔɪ/.
Answer:C. coin