题干

下列方程式正确的是(   )

A:用氯胺处理自来水:NH2Cl+H2ONH2OH+HCl

B:在含有Mg2+、HCO3-的自来水中加入过量的澄清石灰水:
Ca2+ +Mg2+ +2OH- +2HCO3-=CaCO3↓+MgCO3↓+2H2O

C:长时间煮沸含Mg2+、HCO3-的自来水:Mg2+ +2HCO3-Mg(OH)2↓+2CO2

D:Na2FeO4既是混凝剂、又可作消毒剂,作混凝剂的作用原理为:

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C

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    People are compassionate. With effort, we can translate compassion into action. An experience last weekend showed me this is true. I work part-time in a supermarket across from a building for the elderly. These old people are our main customers, and it's not hard to lose patience over their slowness. But last Sunday, one aged gentleman appeared to teach me a valuable lesson. This untidy man walked up to my register (收款机) with a box of biscuits. He said he was out of cash, had just moved into his room, and had nothing in his cupboards. He asked if we could let him have the food on trust. He promised to repay me the next day.

    I couldn't help staring at him. I wondered what kind of person he had been ten or twenty years before, and what he would be like if luck had gone his way. I had a hurt in my heart for this kind of human soul, all alone in the world. I told him that I was sorry, but store rules didn't allow me to do so. I felt stupid and unkind saying this, but I valued my job.

    Just then, another man, standing behind the first, spoke up. If anything, he looked more pitiable. “Charge it to me,” was all he said.

    What I had been feeling was pity. Pity is soft and safe and easy. Compassion, on the other hand, is caring in action. I thanked the second man but told him that was not allowed either. Then I reached into my pocket and paid for the biscuits myself. I reached into my pocket because these two men had reached into my heart and taught me compassion.