—__________ do I have to change the robot’s batteries? —Every two months.
A. How long B. How soon C. How often D. How many
Mr Chen __________ his mobile phone to the shop because it can’t work at all.
A. need to return B. needs return C. need returning D. needs to return
Computers have made a great difference _______ our everyday life.
A. with B. of C. to D. for
After half a day’s hard work, we made our classroom look as _______ as new.
A. well B. better C. best D. good
_______ provides many hours of air for astronauts in space.
A. An air tank B. A power pack C. A helmet D. A space sleeping bag
We are wondering ________ we can prevent people from polluting the earth.
A. who B. that C. whether D. what
