He is majoring in psychology.

Gaku is my best friend.

He has a deep interest in archaeology.

He likes to take a walk in the park at dusk.

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.