Whatareyougoingtodotomorrow？We'llgotothelibrarytomorrowifit______．（）A.isn'trainB.rainC.won'trainD.doesn'train

　　What are you going to do tomorrow？We'll go to the library tomorrow if it ______．（）

　　A.isn't rain

　　B.rain

　　C.won't rain

　　D.doesn't rain