Question

Read the text below. For each empty space (1-12) choose the correct answer (А, В, C or D). Recently scientists (1) more about life on planet Earth and now they (2) better where to look for life in outer space.
For a long time, scientists (3) that life (4) on sunlight for energy. Then, in 1978, a submarine (5) to the bottom of the Pacific Ocean. Although there (6) no sunlight, they (7) tube worms, clams and crabs, and other life forms.
Since then scientists (8) at the life on earth in other difficult environments — dry, cold and hot - and (9) that water is the key. Wherever there (10) water, life (11) exist. So scientists (12) to search for water in the solar system.

A В C D
1 found out has found out find out have found out
2 knew have known know known
3 believe believed believes have believed
4 depended depend depends have depended
5 dive have dived has dived dived
6 were was has been have been
7 have found finds found has found
8 have looked looked looks has looked
9 found have found has found finds
10 was has been is be
11 could will be able was able can
12 began has begun have begun begin