Is that his uncle的复数形式

Is that his uncle的复数形式 that is his uncle 的复数形式是什么 That is his brother的复数形式 is that his key (改为复数形式) that is his sister改为复数形式 uncle的复数形式 Is that man his uncle? Is that his class?怎么变成复数形式? That is his uncle.用his uncle提问 is that her counsin 的复数形式 Is that a photo?的复数形式 This is his sister and that is his son.怎么改为复数形式