It was()it rained heavily that they didn't come.A.as B.becauseC.forDsince 为什么不选C

问题描述:

It was()it rained heavily that they didn't come.A.as B.becauseC.forDsince 为什么不选C

for后面加名词结构,不能加一个句子,而because后面可以加句子.
如果是以下这样也对.It was for the rain that they didn't come.