These trainers are under the bed.改为单数形式

These trainers are under the bed.改为单数形式 these are new books.改为单数形式 these are chinese books 改为单数形式 are these apples?改为单数形式 Are these sheep怎么改为单数形式 Are these your cousins改为单数形式 These are English books.改为单数形式 are these your books?改为单数形式 these are apples 改为单数形式 These are cakes 改为单数形式 These are apples改为单数形式 these pairs of tramers are under the trees 改为单数句