The president did much for world peace. That was he was awarded the Nobel Peace Prize.A.

问题补充：

The president did much for world peace. That was he was awarded the Nobel Peace Prize.

A. when

B. what

C. because

D. why

答案：

A. when

B. what

C. because

(答案→)D. why

解析：句意：这个总统对世界的和平做出重大的贡献，那就是他为什么被授予诺贝尔和平奖的原因。A. when什么时候，B. what 什么，C. because因为，D. why为什么，所以选D。