this is a box改为复数

This is a box.改为复数形式 this is a box改为复数 1.This is a box.(改为复数形式) this’s a boxs. 1.This is a box.(改为复数形式) this’s a boxs. That is a box 改为复数句子 This is a box and that is a knife （改为复数句） This book is in that box.（改为复数形式） This is his pencil-box.改为复数句子怎么改? __what is it _IT is a box改为复数句 This is a box and that is a knife.改为复数形式〔怎么变的〕 What is this? It is a box.复数形式 Is's a pencil-box.改为复数句 it is a box.(改为复数形式）帮忙啊! It is a large box.(改为复数句） That is a box 改为单数或则复数 what isit?lt is a box改为复数句 This is a box.(改为复数句）是These are boxes.还是These are many boxes. this is a box.变复数句___________?