把下列各句变成复数形式

(1)I am a student.
We are students.
(2)This is my frind
These are our friends.
(3)She is a coustoms office(海关人员）
They are coustoms offices.
(4)My case is broun(棕色）
Our cases are brown.
(5)What colour is her hat?
What colour are their hats?
(6)Is this your blouse?
Are these your blouses?
(7)Here is my possport.
Here are our possports.
(8)Whose shirt is this?
Whose shirts are these?
(9)It is an English car.
They are English cars.
(10)He is an engineer(工程师）
They are engineers.