The scientific research on how to protect the rare animals is ________. Many scientists are working hard to find new way to raise the animals by man.

We forgot both of the ____.

To our credit         , China overcame all the difficulties caused by the disasters in 2008 and successfully hosted the 29th Olympic Games.

He knows so much about Russia that he's universally acknowledged as a(n) _____ on Russian affairs.

A study shows that walking fast in your old age is a ______ that you will live a long life.