I don't know____he will come tomorrow.Don't worry.____he comes.I'll let you know

问题描述:

I don't know____he will come tomorrow.Don't worry.____he comes.I'll let you know
A.whether.If B.if,Whether C.when,Whether D.that,if

A 因为whether与前面的句子不要用逗号隔开,而if却要用逗号隔开.