The conference will be put off until next week we will have made all the preparations.A.

问题补充：

The conference will be put off until next week, we will have made all the preparations.

A. which

B. in which

C. when

D. on which

答案：

A. which

B. in which

(答案→)C. when

D. on which

解析： 这题考查定语从句，先行词是next week，定语从句中不缺主宾表，所以用when引导定语从句，修饰next week，句意是：会议将被推迟到下周，那时我们都会准备好了。选C。