Question

6. The tourists were talking with each other excitedly so the guide had to raise her voice          . (herself)

游客们正聊得兴奋，所以导游不得不提高音量让游客听到她讲话。

Answer 1

6. to make herself heard (by them) 此处是不定式作目的状语，herself和hear之间是动宾关系，所以用过去分词heard表被动。