We can see different signs in public places．Some____tell us what we should do．This sign is____．There is a picture of an animal in the____．It tells us to look out for animals．Some signs tell us what we should not do．We should not smoke in the forest．It____start a fire．That's why we see a "____" sign in the forest．Some signs tell us where to go．The bus and underground signs tell us where to find the stations．

阅读下列材料:

材料一 西周时,耒、耜是主要农具,“一人跖(踏)耒而耕,不过十亩”。战国时,李悝说:“今一夫挟五口,治田百亩,岁收亩一石半,为粟百五十石。”

材料二 中国农村原本是一个自治的社会,“皇权不下县,县下是宗族,宗族皆自治,自治出于伦理”,几千年来都是如此。广大农民“交了粮,自由王”,强制他们的力量也并不多。相反,小农们对封建国家有很强的约束力,直接决定着社会的治乱、经济的衰荣。——李成贵《国家、利益集团与三农困境》

请完成:

要验证锌、铁、铜三种金属的活动性顺序，可选用下列哪组试剂（　　）