按要求完成下列各句

1. What is the most useful invention?  Do you think?（合并为一句）   

                                         is the most useful invention?

2.Li Lei asked me to go to his birthday party.（改为被动语态）  

I                      to go to Li Lei's birthday party.

3. The car was invented in 1885.（对画线部分提问）   

                     the car           ？

4. The workers were made to finish the work at once by the manager. （改为主动语态）    

The manager            the workers            the work at once.

5. We must do something to protect our environment.（改为被动语态）   

                                          to protect our environment.

直角尺常用于检验零部件平面间的（）。

A.平行度

B.位置度

C.对称度

D.垂直度