问题

Storms most commonly occur_______a warm air mass and a cold air mass touch each other.

A:in case
B:where
C:in which
D:unless

正确答案是：

同类题型

Cindy’s brother a ping-pong bat.

He started to work dilligently _____ he came up with the idea of hybrid rice for the first time in the 1960’s

14 He _____ a visit to the factory and waswarmly _____ by the workers there

Students are required to go out in couples, especially in the evenings, with friends ______ they get into trouble

My brother has been teaching ________ he was 21 years old.