把they are boxes.改为单数句怎么改

把they are boxes.改为单数句怎么改 -What are those?-They are pencil-boxes.(改为单数句） These are boxes. (改为单数句） 把They are apples.改为单数句 They are my boxes 改为否定句 There are oranges in the boxes.改为单数句 Those are old boxes. (改为单数)_____ ______ old ______. they are apples改为单数 they are waitresses(改为单数 There are some children helping the old 改为单数句 There are some boxes of bananas 改为单数句 Are they students?（改为单数句） What colour are they?改为单数句 are they apples?改为单数形式 they are English books.(改为单数形式) Are they American cars?改为单数 为啥 They are his friends改为单数形式 Are they bookcase 怎样改为单数句? are they american students?改为单数形式