请高手详细回答为什么选d?我选的a为什么错了?16._______ his mother out,he had to stay at home alone.A.As B.For C.Because D.With

请高手详细回答为什么选d?我选的a为什么错了?16._______ his mother out,he had to stay at home alone.A.As B.For C.Because D.With
请高手详细回答为什么选d?我选的a为什么错了?
16.
_______ his mother out,he had to stay at home alone.
A.As B.For C.Because D.With

请高手详细回答为什么选d?我选的a为什么错了?16._______ his mother out,he had to stay at home alone.A.As B.For C.Because D.With
as作为由于,因为的时候需要跟句子