问题
选择题
---Why did the teacher get angry? --- __________ what we had done the day before.
A．Because
B．Since
C．As
D．Because of
答案
答案：D
考查介词短语。because of 是介词短语，后接名词、代词或者接名词性从句。而在此处是有what引导的名词性从句，相当于一个名词，所以用because of。