Is that his sister?变为复数句

Is that his sister?变为复数句 that is his sister改为复数形式 that is his pen变复数句 that is his room 变复数 That is his brother变复述形式 Thsae are his brothers（变单数形式） That's his friend（变复数形式） Is this your sister?(做否定回答) Those are my friends,(变单数形式) His sister,always is his sister. his sister is This is his sister and that is his son.怎么改为复数形式 That is his parents That is his sister This is my brother These are my friend 以上改一般疑问句 Is that ( ) your sister This is his sister and that,s his son.怎么改为复数形式 that is his pen变一般疑问句并否定回答 His sister like cat变否定句 she is his sister,helen. is this your father?否定回答 that is his sister?复数句 把these are my ruler改为一般疑问句后是什么?还有这几道题：this is her sister(变复数形式）that is my dictionary(变为复数形式)those are his books(变为单数） Is that girl his sister?（作肯定回答） Is helen his grandmother?（作否定回答）