Although Albert Einstein would someday be _________ famous scientist, he did not like __________ school.

A．a; 不填

B．a; the

C．the; 不填

D．the; the

在正投影图的展开中，A点的水平投影a和正面投影a′的连线必定（）于相应的投影轴。

A.平行

B.倾斜

C.垂直

D.投影