题目

黑色人种主要分布在非洲，这主要是受( ) A . 海陆位置的影响 B . 河流的影响 C . 气候的影响 D . 地形的影响 答案：C －How come your father can read books in German? －Well, he ________ on a project with some German engineers for 3 years when he was young． [　　] A． worked B． has worked C． had worked D． would work