松鼠将松子埋藏在地下，在适宜的条件下，埋藏的松子就会萌发，这体现了动物在生物圈中的作用是（  ）

根据下列图示所给信息回答问题．

（1）图一是氟、氯原子的结构示意图．氟、氯属于两种不同的元素，他们的本质区别是____ 不同；氟元素和氯元素化学性质相似的原因是____ ．

（2）图二为甲和乙反应生成丙的微观图示（“”和“分别表示不同元素的原子）．甲、乙、丙三种物质中，属于单质的是____；甲和丙两种物质化学性质不相似的原因是____．

    In our town, there is a big zoo with a lot of animals in it. There are so beautiful tigers and two old lions. They eat a lot of meat every day.
There are also two big elephants and one baby elephant. The elephants are kind animals. They eat a lot every day. They like children. Children often give them bread and bananas. Elephants like bananas best.
    In our zoo there are also brown bears, black bears and white bears. They stand on their hind legs, hold up their four legs and ask for food. They like cakes very much.
    There's also a children's corner in our zoo. Children ride horses and donkeys and watch the monkeys there. The monkeys are very funny. They climb up ropes and jump down again and play with each other like small children.

在中国近代，下列哪一条约签订以后出现了下图局面（       ）

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