My friend John insisted that he had seen ______ alien the day before.

   A. a    B. an    C. some     D. any

It is hard to imagine what life __________ in 100 years.

   A. will like   B. will be like   C. likes   D. might like

The gravity on Mars is only about ________ of that on Earth.

   A. 1/2    B. 2/3     C. 1/8    D. 3/8

We are wondering ________ we can prevent people from polluting the earth.

   A. who    B. that    C. whether     D. what

_______ 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

After half a day’s hard work, we made our classroom look as _______ as new.

   A. well   B. better    C. best     D. good

Computers have made a great difference _______ our everyday life.

   A. with   B. of    C. to    D. for

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

—__________ do I have to change the robot’s batteries? —Every two months.

   A. How long   B. How soon   C. How often    D. How many

The Nanjing Yangtze River Bridge is still very strong, ___________ it is almost 43 years old.

   A. although   B. but    C. so    D. because