He was trying to put across his ideas to his audience. A. to convey B. to cross C. to influence D. to convince

B. to cross means to go over or across something. This does not make sense in the context of the sentence.

C. to influence means to have an effect on someone or something. This could be a possible answer, but it is not as specific as A.

D. to convince means to persuade someone to do something. This is not the best answer because the speaker is not trying to persuade his audience to do anything. He is simply trying to communicate his ideas.