A.9 个   B.10个   C．无数个．

以化合价为纵坐标，以物质的类别为横坐标所绘制的图像叫价类图。如图为铁的价类图，例如E点可表示+2价的亚铁盐。请回答：

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A点表示的物质所属的物质类别是____ 。
请写出B点表示的物质化学式____ 。
已知C点表示的化合物在常温下能与氧气．水发生化合反应生成D，写出相应的化学方程式____ 。

将一个质量为2kg的物体以10m/s的速度从距地面为10m的高度抛出．取g=10m/s²求：

    Around twenty years ago I was living in York. 1 I had a lot of experience and a Master's degree,I could not find 2 work.

    I was 3 a school bus to make ends meet and 4 with a friend of mine, for I had lost my flat. I had 5 five interviews(面试) with a company and one day between bus runs they called to say I did not 6 the job. “Why has my life become so  7？”I thought painfully.

    As I pulled the bus over to  8  a little girl, she handed me an earring  9 I should keep it  10  somebody claimed (认领) it. The earring was painted black and said “BE HAPPY”.

    At first I got angry. Then it  11 me—I had been giving all of my 12  to what was going wrong with my 13  rather than what was right！I decided then and there to make a 14 of fifty things I was happy with. Later, I decided to15 more things to the list.That night there was a phone call for  16  from a lady who was a director at a large  17.She asked me if I would  18  a one­day lecture on stress(压力) management to 200 medical workers. I said yes.

    My 19  there went very well, and before long I got a well­paid job.To this day I know it was because I changed my way of  20  that I completely changed my life.