①2H   ②2NH₃③SO₂④O₂⑤Mg²⁺⑥2OH^﹣⑦H₂O．

中国龙文化，源远流长。龙的形象深入到了社会的各个角落，龙的影响波及了文化的各个层面，多彩多姿。关于龙的形象，自古以来就有“角似鹿、头似驼、眼似兔、项似蛇、腹似蜃、鳞似鱼、爪似鹰、掌似虎、耳似牛”的说法。这表明（   ）。

①一切观念都是现实的模仿和被动的反映  

②任何观念都可以从现实世界中找到其物质“原型”  

③虚幻的观念是对事物本质的正确反映  

④观念的东西是移入人脑并在人脑中改造过的物质的东西

A

Dear Simon,

    Here is something about my weekdays and weekends.

    Monday? Oh, I don't like Monday because I have to go back to school again after the weekend. Tuesday is not so bad. I usually play tennis with my friends after school. On Wednesday evening I don't go out. I stay at home and do my homework. I like Thursday best because the next day is Friday. I always go out on Friday — maybe go to the cinema, go to a disco or do some other things. I love the weekend. On Saturday I stay in bed until lunchtime. And then I go shopping in the afternoon. In the evening I go to a club, and there are good bands every Saturday. Then on Sunday I go to my friend's house or he comes to mine. I usually visit my grandmother for an hour in the afternoon. Then the weekend is over and it is Monday. And I feel bad again!

    Write to me soon and tell me about your weekdays and weekends.

Best wishes!

David