It was early morning in London Prime Minister Cameron arrived to give his speech.
A. where
B. when
C. while
D. that
网友回答
A. where
(答案→)B. when
C. while
D. that
解析：本题中后面的从句并不缺少主语和宾语，故用关系副词来引导定语从句，先行词early morning指代的是时间，故用when来引导，作时间状语。句意：在伦敦，卡梅伦首相很早就到达来发表他的演讲。