Then make sentences. We use this/these/that/those in the singular and this/these/that/those in the plural. We use this/these/that/those

We use this in the singular and these in the plural. We use that in the singular and those in the plural.

This is a pen. — These are pens.

This is a flower. — These are flowers.

This is a window. — These are windows.

This is a dog. — These are dogs.

This is a cat. — These are cats.

This is a rat. — These are rats.

This is a green tree. — These are green trees.

This is a high building. — These are high buildings.

That is a mouse. — Those are mice.

That is a yellow leaf. — Those are yellow leaves.

That is a good singer. —  Those are good singers.