勉強中

彼(かれ)は勉強中です。

He is doing his work.

彼(かれ)は勉強中であった。

I found him at his books.

勉強中に邪魔をしないでくれ。

Don't distract me while I am studying.

彼(かれ)は勉強中に寝入ってしまった。

While he was studying, he fell asleep.

生徒たちは今(いま)みんな勉強中です。

The students are all at their desks now.