Ответ:

(1).   Earth is the name of the planet on which we (C) live.

(2).   It is a huge ball of rock (B) spinning through space.

(3).   No one is sure when earth (A) began, but some scientists think that, between 10 and 20 billion years ago,

(4)   there (A) was a huge explosion,

(5)   (D) has called  the big bang.

(6).  Gradually, over millions of years, stars and planets (A) have started to form.

One of these planets was Earth.

Объяснение:

     A                          В                          C                                D

1 are living              lived                    live                        have lived

2 spin                   spinning               span                       is spinning

3 began                begins                 begin                         begun

4 was                     were                have been                       is

5 calling                was called         called                        has called

6 have started      started              was started               starts