Use the verbs in the appropriate forms. scientists use lots of different methods to explore our planet and to learn about its past, but we still have very little information about ourselves. our primitive ancestors (appear) on the earth about six million years ago. they (not look) like people. they looked more like apes. people (homo sapiens) (live) here for only about two million years. we (make) amazing progress from a creature with a stone axe to someone who's able to leave the earth on a spaceship and travel to the other planets. but our history is a very short period of time on the timeline of the planet. before us the earth looked different. the plants were huge and large areas (cover) with forests. if we (have) a time machine, would you like to go to the past and see everything with your own eyes? it would be great to see a living dinosaur, wouldn't it
didn't look
have been living
have made
were covered
had