根据如图中所示装置回答下列问题．

（1）用大理石和稀盐酸制取二氧化碳时，可选用的收集装置是　____ 　（填字母，下同），并写出反应发的化学方程式　____ ．

（2）用高锰酸钾制取氧气时，装置A还需要做的一点改动是____ ．

（3）实验室制取气体用B装置制气体应满足的条件是____ ．

阅读下列短文，从下面每小题的A.B.C .D四个选项中选出最佳选项。

    It is easier to float in the ocean than in a swimming pool. Do you know why?

    Ocean water is full of salt - and salt water can hold up more weight than fresh water. See for yourself! (Ask an adult to help you.)  You will need: 3 cups warm water; A wide-mouth jar（罐）; Salt; A spoon; A potato. You will do: 1. Pour 1.5 cups of warm water into the jar. 2. Add 1/3 cup of salt.  3. Stir(搅拌) until the salt is completely dissolved(完全溶解) 4. Add another l.5 cups of water. Pour it slowly over the back of the spoon into the jar so that the two kinds of water will not mix together. 5. Softly place the potato into the jar. Don't drop it. What will happen: The potato will sink - but only halfway! Why: Salt water is heavier than fresh water, so it will stay on the bottom. The fresh water will remain on the top. The potato is heavier than the fresh water, but it is lighter than the salt water. That is why the potato will sink only halfway down.

中国近代史既是一部中华民族的屈辱史，也是一部中国人民的抗争史。

请回答：

下列运算中，错误的是（    ）
①$\sqrt{1\frac{25}{144}}=1\frac{5}{12}$;②$\sqrt{{\left(-4\right)}^2}=\pm 4$;③$\sqrt{-2^2}=-\sqrt{2^2}=-2$;④$\sqrt{\frac{1}{16}+\frac{1}{25}}=\frac{1}{4}+\frac{1}{5}=\frac{9}{20}$.