These are old buses.的单数句

These are old buses.的单数句 These are buses单数 are these old coats 改为单数句 These are Chiese buses.变为单数形式 Is this a bike?(做否定回答) __,it __.Are these buses?(改为单数意义的句字) These are some old photos.改为单数句 Are these your ruler?的单数句是什么 考试题!There are many buses的单数形式. these toothbrushes are new.改单数句 Are these nice pictures 改为单数句 are these your erasers?改单数句 are these men doctors 单数句