I__upset when i failed in the exam.

题目

I__upset when i failed in the exam.
A be B used to was C use to be D used tobe
回答时候请回答为什么谢谢

答案

C 首先A是原型,排除.B的格式不正确,used to 后面要用动词原型的；后面的when i failed in the exam是过去式,因此主句要表达出“过去···”的意思.use to do sth正好可以表达这层意思