watch （复数） key（复数） library（复数） card（复数）

watches （复数） keys（复数） libraries（复数） cards（复数）
Is that your watch?
Are they yours?
There is a computer game machine in the school library.
There are some keys in the 7E classroom.
再问： This is my friend（改为复数形式） Is that your sister?（改为复数形式） Tese are my brothers brothers（对划线部分提问） These two girls are my sisters? my sisters（对划线部分提问） TThey are his daughters his daughters（对划线部分提问） This is a photo of my family（改为复数形式）
再答： These are my friends. Are those your sisters? Are these your brothers? Are these two girls your sisters? Who are they? These are the photos of my family.