用所给词的适当形式填空。

1. Edison is one of the greatest ________ (invent) in the world.

2. The gravity on the surface of Mars is about one ________ (three) as strong as it is on the earth.

3. Six books have been written by her, ________ (include) the story book.

4. This railway line _________ (connect) London to Edinburgh.

5. Scientists think that there _________ (be) life on the earth for millions of years.