题干
— Did Peter fix the computer himself?
— He ________, because he doesn't know much about computers.
— He ________, because he doesn't know much about computers.
A：has it fixed
B：had fixed it
C：had it fixed
D：fixed it
答案(点此获取答案解析）
C
与曲线
在点P（1，1）处的切线互相垂直，则