11.   The blue whale is the largest creature that has ever existed on earth.

12.   The constitutional rights of the people which exist on paper were withheld for the sake of national unity.

13.   The new evidence seemed to indicate that life existed on Mars billions of years ago.

14.   They exist on a diet of fish.

15.   Upland masses exist on either side of a central rift valley.

16.   Vologsky was like a zombie, existing on the outermost fringe of sentient life.

17.   The hostages existed on bread and water.

18.   ...the problems of having to exist on unemployment benefit.

19.   It is possible that life exists on other planets.

20.   Does life exist on Mars?