We had to stay at home it was raining hard.A. ofB. becauseC. because ofD. as

问题补充：

We had to stay at home it was raining hard.

A. of

B. because

C. because of

D. as

答案：

A. of

(答案→)B. because

C. because of

D. as

解析：句意：我不得不待在家里，因为下很大的雨。Because因为，后接从句；because of因为，后接名词性短语；题中后面是个从句，故选B。