In mathematics, equivalence classes are a very important concept.

He is a gambling addict, causing trouble for his family.

He started digging a trench.

He is a very famous artist.

My apartment is covered with a relatively small tatami mat.

I take a walk in the park every day.

A journey of a thousand miles begins with a single step.

He shot down the enemy's fighter plane.

Alkaline earth metals are one of the main components of the earth's crust.