Eva decided to take a second course since she ____ the first one.
问题描述：
Eva decided to take a second course since she ____ the first one.
A.has completed B.is completed C.had completed D.will complete 我知道选C但需要解释为什么不选A?
答
前面不是有decided吗,就说明是在过去决定选第二门课程,原因是过去的过去已经通过了第一门,过去的过去就是过去完成时