This structure has existed for centuries.

He is an expert in mineralogy.

He is an expert in paleontology and is researching dinosaurs.

He is an expert in nuclear physics.

In chemistry class, I learned about basic oxides.

In chemistry class, I learned about acidic oxides.

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.

This factory strictly controls the emission of hydrogen sulphide.