They are my best friends.

There is a serious conflict between them.

The problem came about suddenly.

This problem is very serious.

Do you understand the seriousness of this problem?

While he was taking a nap, I finished my homework.

He took a little pause before speaking.

During summer vacation, I will go to the beach.

A gap is created in the wall of the building due to the earthquake.

There is a secret between him and me.