He is writing a thesis on celestial mechanics.

The government decided to crack down on illegal activities.

He learned to discard unnecessary things.

The tree is the biggest tree in the park.

He is an expert in astrophysics.

He has a deep interest in classical literature.

He is good at fighting using the Tekkō-kagi.

He reads five books every day.

He retracted his previous remarks.

I want to go to Thessaloniki in Greece.