Chemical pollution has a serious impact on the health of the Earth.

This shirt is made of chemical fiber.

My child attends a supplementary school every Saturday.

There are innumerable books in his room.

My hamster is very cute.

Williams is my best friend.

He is a distinguished person in his field.

The debtor has an obligation to repay his debt.

My grandfather is already sixty years old.

When summer vacation comes, the children enjoy bug catching every day.