if I were you,I would study math harder
If there were no air or water,there would be no living things on the earth.
如果没有水和空气,地球上就不会有生物.(事实：地球上既有空气也有水)
If I had any money with me,I could lend you some.
如果我带钱了,我就会借给你些.（事实：没有带钱）
If he studied harder,he might pass the exam.
如果他再努力些,就能通过考试了.（事实：没有努力）
If I were you,I'd wear a shirt and tie.
如果我是你,我就会穿衬衫和领带.(事实：我并不是你）