It is well known to all that water enough can change into ice quicklyA. if coolingB. t

问题补充：

It is well known to all that water, enough, can change into ice quickly．

A. if cooling

B. though to be cooled

C. when cooled

D. when is cooled

答案：

A. if cooling

B. though to be cooled

(答案→)C. when cooled

D. when is cooled

解析：考查状语从句的省略。句意：我们都知道，当水足够冷却，很快就会变成冰。应用when cooled，中间省略了it is ，所以选C。