题目内容：

if you don't be careful,you will fail in the exam.和if you aren't careful.哪个对?
if you don't be careful,you will fail in the exam.和if you aren't careful,you will fail in the exam.

优质解答

正确的是：if you aren't careful,you will fail in the exam.

追问：

为什么？

追答：

除祈使句外，be动词的否定并不是在前面加don't