She suggested a skilled worker _____ to get the machine _____.

　 A. send for; repair 　 B. be sent for; repaired
　 C. sending for; repairing 　 D. be sent for; to repair

An early typewriter produced letters quickly and neatly; the typist, _____ couldn't see his work on his machine.

　 A. however　 B. therefore　 C. yet　 D. although

_____ troubles me is _____ I don’t know _____ is to be done with the new machine.

　 A. What; what; that　　　　　　　 B. What; that; how

　 C. What; that; what　　　　　　　 D. What; because; which

It is master Wu who taught us __________ the machine.

　 A. what to do with　　　　　　 B. ran

　 C. how to run　　　　　　　　　 D. how could run

The new machine，if _________ properly，will work at least ten years.

　 A. use 　 B. using   C. being used 　 D. used