Question

We studied the _____ of famous scientists.

A
life

B
lifes

C
lives

The three ______ played together all afternoon.

A
children

B
child

C
childs

The three _____ were gigantic.

A
moose

B
mooses

C
moosses

Answer 1

1) C — lives. ("We studied the lives of famous scientists.")
2) A — children. ("The three children played together all afternoon.")
3) A — moose. ("The three moose were gigantic." — "moose" is the same in singular and plural.)