He was staring at me with a deadpan expression.

His eyeballs widened in surprise.

By regularly checking the key performance indicators, you can understand the performance of the company and devise improvement measures.

He is majoring in linguistics.

He has a deep interest in astronomy.

He is an expert in physics.

Electromagnetism is a part of physics that studies the interaction between electricity and magnetism.

He is good at solving geometry problems.

He is an expert in toxicology and conducts many studies.

He is an expert in mythology and gave a lecture on the gods of ancient Greece.