There is a big tree in front of the library.

He parked his car in front of the house.

My keys are inside the house.

He is quite a good cook.

I think his Japanese has improved quite a bit, hasn't it?

I am busy with work during the daytime.

This phenomenon occurs cyclically.

She is emotionally unstable, getting angry or crying easily.

This is my first question.

An isotope refers to elements with the same atomic number but different numbers of neutrons.