The police used fingerprints to identify the criminal.

In mathematics, equivalence classes are a very important concept.

It's very easy to walk on this flat road.

The initial response when an earthquake occurs is very important.

My brother is a master of Taido.

We belong to the same class.

This statue is made of copper.

He found an old copper coin.

He is an expert in ethology, and his research is highly regarded worldwide.

He always keeps in mind the phrase 'If one learns without thinking, it is a waste.'