6 a What's up there

Sam wants to become a(n) ____ because he loves studying the stars.

That ____ star up there is called the North Star.

How can you ___ that you're telling the truth?

Just look at the ___ of the water and you'll see that the river is polluted.

Some astronomers in the past thought that the Earth was the centre of the ___.

Where do you think the best ___ for the sofa is?

There's a(n) ___moon out tonight.

___ USA is a big country in North America.

The capital of the USA is __ Washington, DC.

Canada is to ___ north of the country.

__ longest river is __ Missouri.

To __ east and west of __ country lie __ Atlantic and __ Pacific Ocean.