单选题：He made a mistake, but he corrected the situation_________ i..

Work hard________ you will succeed.[ ]A. andB. so C. orD. or not

She found her calculator ________ she lost it.[ ]A. whereB. whenC. in whichD. that

What the doctors really doubt is ________ my mother will recover from the serious disease soon.[ ]A. whenB. ifC. whetherD. what

He is ready to help others, seldom, ______ refusing them when they turn to him.[ ]A. if never B. if ever C. if not D. if any

It’ll be 3 days _____ he _____ back from his hometown.[ ]A. when; will comeB. after; will comeC. since; comesD. before; comes