if做是否的时态

　　Put your hand up if you need more paper.

　　若有人还要纸，请举手。

　　He must be 70 if he's a day!

　　他至少70岁了！

　　I don't care if I never see him again!

　　即使我永远再也见不到他，我也不在乎！

　　If that's what you think, you're way off base.

　　你如果那么想就全错了。

　　Call me if you have any problems regarding your work.

　　你如果还有什么工作方面的问题就给我打电话。

　　What difference will it make if he knows or not?

　　他知不知道有什么关系吗？