Now their talks have reached a key stage one side must give in to the other.A. whichB. th

问题补充：

Now their talks have reached a key stage one side must give in to the other.

A. which

B. that

C. when

D. where

答案：

A. which

B. that

C. when

(答案→)D. where

解析：考查定语从句。本题的定语从句的先行词是a key stage，后面的定语从句句子很完整，故使用关系副词的形式。C项是指时间。故D正确。句意：现在他们的谈话到了一个关键的阶段，在这个阶段一方必须向另外一方作出让步。故D正确。