【2012重庆卷】It was 80 years before Christopher Columbus crossed the Atlantic______ Zheng sailed to East Africa
| A．when | B．that | C．after | D．since |
By the time Jack returned home from England，his son ________ from college.(2011·辽宁)
| A．graduated | B．has graduated |
| C．had been graduating | D．had graduated |
In the last few years thousands of films ________ all over the world.
| A．have produced | B．have been produced |
| C．are producing | D．are being produced |
— Alvin，are you coming with us?
—I'd love to，but something unexpected ________.
| A．has come up | B．was coming up |
| C．had come up | D．would come up |
—I remember you were a talented pianist at college.Can you play the piano for me?
—Sorry，I ________ the piano for years.(2012·湖南)
| A．don't play | B．wasn't playing |
| C．haven't played | D．hadn't played |
—Look！Somebody ________ the sofa.
—Well，it wasn't me.I didn't do it.(2012·江西)
| A．is cleaning | B．was cleaning |
| C．has cleaned | D．had cleaned |