There will be a twenty-minute break during the performance people can go to the restroom

问题补充：

There will be a twenty-minute break during the performance, people can go to the restroom or buy some snacks.

A. that

B. where

C. when

D. which

答案：

A. that

B. where

(答案→)C. when

D. which

解析：

这里考查非限制性定语从句，定语从句修饰a twenty-minute break（20分钟的休息时间），所以用when引导定语从句。句意是，在表演中将有20分钟的休息时间，这时人们可以去休息室买点零食。