Which of the following is right?

Which of the following is right?
A.He couldn't find the key for the door.
B.The notes to the text are not easy to be
under stood.
C.Jack worked hard in order to gain the
entrance to medical school.
D.The answer to the question come out wrong.
有三句有语法错误
请先说答案,再把每句错的原因加以分析,并说出每一句考察的语言点
刚刚在"作业帮助"里提问,竟然没人会..
D 选项是came out wrong，（是我打错了，抱歉抱歉）
这题答案应该选D，就不知道C错在哪里了？