because是从属连词，后接原因状语从句。because of是个短语介词，不可以引导原因状语从句，而应该接名词，代词等。because所引导的从句除用作原因状语外，还可用作表语。而复合介词because of所引导的介词短语通常用作状语而不用作表语。
because造句
I didn’t buy it because it was too expensive. 我没有买是因为它太贵了。
He is here because of you (that). 他为你(那事)而来这里。
He lost his job because of his age. 由于年龄关系他失去了工作。
We said nothing about it, because of his wife’s being there. 因为他妻子在那儿，我们对此只字未提。
He knew she was crying because of what he had said. 他知道她哭是因为他说的话。