题目

        Jack is a twenty-year-old young man. Two years ago, when he finished middle school, he found work in a shop. Usually he works until ten o'clock in the evening. He is very tired when he gets home. After a quick supper he goes to bed and soon falls asleep. His grandma who lives downstairs is satisfied with him.     One day, on his way home, he met Mary. They were both happy. He asked the girl to his house, she agreed happily. He bought some fruit and drinks for her. And they talked about their school, teachers, classmates and their future. They talked for a long time. 下列反应的离子方程式正确的是 [　　] A． 电解饱和MgCl2溶液：Mg2+＋2Cl－＋2H2OMg(OH)2↓＋H2↑＋Cl2↑ B． 碳酸氢铵溶液中加入过量氢氧化钠：NH+4＋OH－NH3↑＋H2O C． Na2S溶液呈碱性：S2－＋2H2OH2S↑＋2OH－ D． 小苏打溶液中加入过量石灰水：2HCO－3＋Ca2+＋2OH－CaCO3↓＋CO2－3＋2H2O