It was not until Mum agreed to buy him a computer was his favorite the boy promised t

问题补充：

It was not until Mum agreed to buy him a computer, was his favorite, the boy promised to study hard.

A. that; that

B. which; that

C. that; which

D. which; which

答案：

A. that; that

(答案→)B. which; that

C. that; which

D. which; which

解析：考查强调句型和定语从句。第一空which指代computer 在句中作主语；第二空that与 it was构成强调句型。故B正确。句意：直到妈妈同意给他买他最喜欢的电脑的时候，那个男孩答应认真学习。