He is always hanging out with bad friends. Truly, birds of a feather flock together.

I am planning to go to Inner Mongolia, an autonomous region of China, next week.

I have been to Outer Mongolia.

I have been to Chicago.

The Paleogene period was a very important time in the history of the Earth.

The American continent is where diverse cultures and nature coexist.

My dream is to live in the United States of America someday.

The whooping crane is an endangered species, and it is difficult to see its beautiful figure.

The American red wolf is one of the endangered species.

He likes to take a walk in the park at dusk.