(B)

Li Qiang and Li Gang are brothers. But their living habits (习惯) are different. Now let’s go to Li Qiang’s room. Li Qiang cleans his bedroom every day and puts his things away. Look! There is a computer on the desk. There are two balls under the bed. A guitar and a kite are on the wall. Some books are on the shelf. So he must be a careful (细心的) boy. Now let’s go to Li Gang’s room. The room is not clean. Can we see his clothes on the desk? Oh, yes. We can see a football and a knife on the desk, too. Li Gang never does any cleaning on weekends. So his room is in a mess.

What do you think of Li Qiang and Li Gang? Li Qiang is a good boy. Li Gang must learn from his brother.

同学们整理实验室时，发现一瓶敞口放置且失去标签的白色粉末状药品，实验员老师告诉大家原瓶药品可能是碳酸钠、碳酸钙、氯化钠、氢氧化钠中的一种，同学们对此很好奇，于是他们对这瓶白色粉末的成分做了如下探究：