He checked whether he remembered or not.

Cyclooctane plays an important role in organic chemistry.

He took out a book from the bookshelf at the back of the room.

He read ten books.

I went to the market accompanied by my mother.

My son participates in judo practice every day.

This is an important problem.

It takes twenty minutes to get to my house.

Deuterium is one of the isotopes of hydrogen.

A new polymer was produced by this chemical reaction.