20

We launch space craft and know a lot about our universe, the nearest planets and stars. However, we know surprisingly little about the place we live in, and one of the ………………… mysteries of the planet is the ocean.

GREAT

21

It ………………… a vast area and there are still so many mysteries hidden in its depths!

OCCUPY

22

Everyone knows that life first appeared in the water. Later some of the creatures ………………… out of the ocean onto the land, and the others stayed there.

COME

23

The ocean ………………… a lot since those prehistoric times but it is still a place where life is rich and diverse.

CHANGE

24

Nowadays the ocean ………………… by millions of amazing creatures too.

INHABIT

25

They are tiny and huge, and some of ………………… look as fantastic as aliens from other planets.

THEY

26

Marine researchers wish they ………………… get to the bottom of the ocean to explore it, but unfortunately it is not possible now.

CAN

27

There ………………… no technology yet that can allow people to go so deep under the water.

BE

28

The ocean is still keeping ………………… secrets.

IT