Concept:The sound being tested is the diphthong /aʊ/, as in the word "how".Explanation:Say each option aloud and focus on the vowel sound.• coy = /kɔɪ/• soul = /soʊl/• how = /haʊ/• mode = /moʊd/Only "how" contains the vowel sound /aʊ/.The other options have different vowel sounds such as /ɔɪ/ or /oʊ/.Answer:C. how