在两块相同的玻璃片上，小明同学分别滴一滴质量相同的水，如图所示．观察图中情景可知，他主要研究蒸发快慢是否与（　　）

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中国东北地区的陆上邻国是（   ）

一只跳蚤在第一象限及x轴、y轴上跳动，在第一秒钟，它从原点跳动到（0，1），然后接着按图中箭头所示方向跳动，即（0，0）→（0，1）→（1，1）→（1，0）…，且每秒跳动一个单位，那么第35秒时跳蚤所在位置的坐标是（   ）

    It is Sunday afternoon. Mary goes to do the shopping with her mother. Her mother wants to buy some food for supper. Mary wants to buy a new skirt and some school things. They come to a shop.
   “What does your shop sell?” Mary asks, “A lot of things.” The girl in the shop says. “You can buy food, drinks, clothes in our shop and school things, too.”
   Mary and her mother go in. There are many people in the shop. Mary looks at a nice white skirt.
   “How much is the skirt?” Mary asks the girl in the shop.
   “It’s eighty yuan.”
   “That’s too dear.”
   “What about the green one? It looks nice. And it’s only thirty yuan.”
   “OK, thanks a lot.”
   “You are welcome.”
    After that, Mary buys some school things, too. Here mother buys a lot of food, like bread, cakes, meat and fish. They get home very late.

下列反应的生成物污染空气的是（）