Scientists think that there has been life on Earth for ______ years．

　　A．millions　　B．million of　　 C．millions of D．three millions

Scientists think that there has been life for__31_ of years. However we haven’t found life on other planets _32_ . The earth is a planet and it _33__ around the sun. Seven other planets also go _34_ the sun. The sun and its planets are __35  the solar system. The solar system is a small part of our galaxy.
Scientists __36_ lots of spacecraft to look at other planets in the solar system, and some spacecraft have gone __37_ the solar system. However, no one __38_ any life in space yet.
But why has no one from other planets sent us a message ? Have they tried to send _39_ to us ? _40_so many stars in the universe, are we alone, or is there life out there in space ? We don’t know.

Scientists think that there has been life for__31_ of years. However we haven’t found life on other planets _32_ . The earth is a planet and it _33__ around the sun. Seven other planets also go _34_ the sun. The sun and its planets are __35  the solar system. The solar system is a small part of our galaxy.

Scientists __36_ lots of spacecraft to look at other planets in the solar system, and some spacecraft have gone __37_ the solar system. However, no one __38_ any life in space yet.

But why has no one from other planets sent us a message ? Have they tried to send _39_ to us ? _40_so many stars in the universe, are we alone, or is there life out there in space ? We don’t know.

用方框中所给词的适当形式填空，使句意完整。

1．What do you think is the best___________ for learning English?

2．What ___________ do you often make?

3．Scientists think that there has been life on earth for ___________ of years．

4．Where is the ___________ countryside to your school?

5．You like ___________ classical music，don’t you?

6．Please listen to the teacher ___________．

7．Yon look much ___________ today．

8．Mr Wang looks very ___________．

9．I feel ___________ now．I want to see a doctor．

10．Very soon she was ___________ in bed．