高铁酸钾（K₂FeO₄）是一种新型、高效的多功能水处理剂，受热时发生如下反应4K₂FeO₄ aR+4K₂O+3O₂↑，则a、R分别是（  ）

①葡萄糖    ②淀粉    ③蔗糖    ④麦芽糖    ⑤果糖    ⑥纤维素．

                                                                                    A Nice Clean Plate
   It's Saturday evening. Bruce is having a birthday party. There are a lot of children at the party. They play together for an hour. Then Bruce's mother gives them some food. But she forgets to give Sam any.
   Sam feels wronged(委屈) but then he remembers his mother's words, “Be polite.(礼貌). Don't ask for food.” So he waits for a few minutes, then he holds his plate up over his head and says loudly, “ Does anyone want a nice clean plate?”