this mask is David’s改为同义句 there are some pictures on the wall.改为单数形式

问题描述:

this mask is David’s改为同义句 there are some pictures on the wall.改为单数形式

this mask is David’s改为同义句:David's mask is this.
there are some pictures on the wall.改为单数形式:there is a picture on the wall.