问题

So difficult it to work out the problem that I decided to ask Tom foradvice.[ ]

A: I did find
B: did I find
C: I have found
D: have I found

正确答案是：

同类题型

When electric cars become______, we’ll need to build more charging stations. [ ]

Scientists still wonder whether cloning will help or harm us and where it ____ us

It’s really cold here. I have never experienced such terrible weather in mylife.

He checked out his composition again and again to make sure that no important points had been________.