Question

He realized she was crying ______ what he had sad.

1. A.
   because
2. B.
   because of
3. C.
   as
4. D.
   since

Answer 1

B
考查名词性从句。what he had sad是名词性从句，而连词because, as和since不能引导名词性从句，所以选B，because of ，介词of后面引导的是宾语从句。