There were _____ dark clouds in the sky;it seems as if it is
1个回答

A的话..many a 后面加的是可数名词的单数形式

B和D的意思是一样的...后面加不可数名词

C中masses of既可以接可数名词复数又可以接不可数名词

题中是要选修饰clouds的...cloud是可数名词..自然B.C不可以...A要跟单数形式所以也不可选...所以就选C...