It was not until the end of last year the economy in our country began to develop rapidly

问题补充：

It was not until the end of last year the economy in our country began to develop rapidly.

A. when

B. that

C. which

D. in which

答案：

A. when

(答案→)B. that

C. which

D. in which

解析：句意：直到去年的年底，我们国家的经济才开始快速的发展。it is …that强调句型，

对not until的短语进行强调说明，故选B