Say the sentences in the plural 1)the piano is black.2)she is a ballerina.3)it is a bird.4)he is a teacher.

The pianos are black
They are ballerinas
These are birds
They are teachers

   1)The piano is black. – The pianos are black.
2)She is a ballerina.  - They are ballerinas.
3)It is a bird. - They (These) are birds.
4)He is a teacher. - They are teachers