Concept:The underlined letters in a word tell which vowel sound to listen for. In "say", the underlined "ay" produces the diphthong sound /eɪ/.Explanation:"Say" is pronounced /seɪ/.Its vowel sound is the diphthong /eɪ/.This same vowel sound is found in "bay", which is pronounced /beɪ/.Since "say" and "bay" both contain the same vowel sound, they match.Therefore, the word that has the same vowel sound as the underlined "ay" in "say" is "bay".Answer:B. bay