改成复数形式．4.This is a book.

改成复数形式．4.This is a book. this is a beautiful cat 改成复数形式 Is this yuor brother改成复数形式 this is an apple.改成复数形式 this,that,is改成复数形式 This is my backpack.改成复数形式 Is this a book 改成复数形式 Those are chairs 改成单数形式 What are these 改成单数形式 把This is a box and that is a knife.改成复数形式 lt is a wolf 改成复数形式 this is my pen pal改成复数形式 this boy is my goog frierd改成复数形式 this is a book改为复数形式 This is a dress.改为复数形式 This is a cat.(改为复数形式) This is a box.改为复数形式 This is a photo.复数形式 This is a pen.(改为复数形式) i have a music lesson this afternoon.改成复数形式.