The <span>word in the sentence does the adjective clause modify is letter (</span>C.) babysitter. Adjective clause functions identically with adjectives that uses the indicators such as the pronouns who, whom, which, and that; or the adverbs where, when, and why.
The answer is (B) because they are interested in the person speech so after he gets done they took a moment of silence and then started to cheer him on