He has a very quarrelsome personality.

He gulped down the water, perhaps because he was nervous.

He was hospitalized due to mental derangement.

A dwarf planet is one of the smallest celestial bodies in the solar system.

My older brother is currently working hard on his research as a graduate student.

He took a tranquilizer to calm his nerves.

He is learning English phonetic symbols.

I love biology.

This ring is made of lazurite.

He publicly announced that he is bisexual.