A lot of trees ______ in the country every year．
A．was cut down B．cut down
C．are cut down D．will cut down
_____ he is only 4 years old，he is able to play the piano very well．
A．if B．although C．unless D．until
Working hard ________ the key _________ success of everything．
A．is,to B．is,of C．are,in D．are,for
We feel like ___________ the work as soon as possible．
A．finish B．to finish C．finishing D．finished
The old man lives _______ in the countryside, but he didn’t feel __________．
A．lonely；alone B．alone；lonely
C．alone；alone D．lonely；lonely
He didn’t know English at all, so he can’t understand __________ the machine．
A．what to control B．to control what
C．how to control D．to control how．
