下列实验操作错误的是  (    )

草履虫生活在（  ）

正比例函数是（　　）

    An old porter (搬运工人) had worked for the railway for a very long time. One morning he was standing in one of the big railway stations and waiting for travelers to ask him to help them with their luggage, when he saw a small man running toward the trains with a big bag in his hand.

    The porter watched the man for a few seconds, and the man saw the porter.

At once the small man ran up the porter and said, "Can I catch the 10：35 train to London, porter?" He was breathing very fast, and he seemed worried.

    The old porter looked at him for a moment and then said with a smile, "Well, sir, I'd like to help you, but I can't answer your question because I don't know how fast you can run along rails. You see," he explained, "the 10: 35 train to London left five minutes ago."

乙炔（C₂H₂）气体和氧气反应能产生高温火焰，工人师傅常用氧炔焰切割或焊接金属．乙炔由碳化钙（块状固体，化学式为CaC₂）与水反应生成，同时生成一种白色固体．

【提出问题】白色固体是什么物质？

【做出猜想】小明经过思考认为有以下几种可能：

猜想一：CaO；猜想二：____ ；猜想三：Ca（OH）₂．

他的依据是____ ．

【交流反思】经过同学们交流讨论，认为猜想一不成立．否定猜想一的理由是：____ ．

【进行实验】（一）取少量白色固体放入试管中，滴加稀盐酸，没有观察到____ ，证明猜想二不成立．（二）取少量白色固体加入到水中，取上层清液，____ ，有白色沉淀出现，证明猜想三成立．该反应的化学方程式为：____ 结论：白色固体是Ca（OH）₂．