答案：B

题目分析：考查because 和because of，意思都是因为，because引导句子，而because of引导名词或名词性短语，as意思“作为”，since意思“自从…”，句子意思“他意识到因为他的话她就哭了”，所以选B

点评：注意because 和because of的区别，做题时要细心，句子He realized she was crying because of his words.是个宾语从句，省略了引导词that。