下面哪个句子是混合虚拟语气结构？

A.If I were you， I would not fail.

B.If I had worked harder， I would have passed the examination.

C.If he had worked harder three years ago，he would be in college now.

D.If I were to be a NBA super star， I would help Chinese basketball players to improve their skills.

正确答案：If he had worked harder three years ago，he would be in college now.