He was so ashamed of his failure that he wished he could crawl into a hole.

He inserted his finger into the anus.

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.

They appear to be antagonistic on the surface, but in reality, they are seemingly not part of the same group.

When he had a problem due to his own actions, he remembered the phrase 'chickens come home to roost'.