He is an expert in mineralogy.

He is an expert in paleontology and is researching dinosaurs.

He is an expert in nuclear physics.

Bioweapons are a major threat to humanity.

In this experiment, we will observe the reaction of organic compounds.

In this experiment, we will use various inorganic compounds.

Both of my parents are doctors.

Ryou is my best friend.

I had lunch with my colleague.

My dormitory is close to the school.