--------,or you will fail in the exam

C
这是个常见的句型：
祈使句（动词原形开头,表条件） + and + 陈述句（一般用will + 动词原形）
Work hard ,and you'll catch up with him.
=If you work hard,you'll catch up with him
如果表否定,中间用or
Hurry up,or you 'll miss the train.
=If you don't hurry,you'll miss the train