Concept:Compare the vowel sound of the underlined word with the vowel sound in each option.Explanation:The underlined word has the long vowel sound /ɑː/.Check each option one by one.A. "stern" has the sound /ɜː/.B. "firm" has the sound /ɜː/.C. "sharp" is pronounced /ʃɑːp/, which contains the same vowel sound /ɑː/.D. "ward" has the sound /ɔː/.So only option C shares the same vowel sound as the underlined word.Answer:C. sharp