把下列各句变成复数形式
(1)Iamastudent.
(2)Thisismyfrind
(3)Sheisacoustomsoffice(海关人员)
(4)Mycaseisbroun(棕色)
(5)Whatcolourisherhat?
(6)Isthisyourblouse?
(7)Hereismypossport.
(8)Whoseshirtisthis?
(9)ItisanEnglishcar.
(10)Heisanengineer(工程师)