-where were you when the UFO arrived?-I was _______ the library.A.at the front of B.in front of

问题描述:

-where were you when the UFO arrived?-I was _______ the library.A.at the front of B.in front of

B in front of
在.前面【在范围外】
at the front of 是在某一范围内的前面