Людмила8 лет назад
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.