如图，双曲线y= (k≠0)上有一点A，过点A作AB⊥x轴于点B，△AOB的面积为2，则该双曲线的表达式为____.

关于公元前3000-前1700年世界其他地区人类生活的变化，我们所知的要少得多。在中国文明即将诞生的黄河中游地区，相当稠密的农业人口形成了，他们以粟为主要食物。甲这些农民在一种特殊的土壤“黄土”上耕作，这种土壤由冰川时期的风吹来的尘土

沉积而成，因此容易挖掘。黄土地区森林不多，因此，耕作技术与中东的刀耕火种大相径庭。正因如此，加上粟在其他地方不是重要作物，所以大多数学者认为，中国的农业独立于中东农业而兴起，虽然中东独特的作物小麦和大麦也从很早的时候就在黄土地区培植了。

在更南部的东南亚大河流域，公元前2000年代，另一种截然不同的农业也取得了更大的发展。【乙】在这些地区，季风是决定性因素：一年中有半年下雨。实际上这半年几乎天天下雨，其他时间则是干旱。雨季和旱季的明显交替意味着当地有洪涝，然后是土地逐步干旱。丙各种根茎作物天性都适合这种气候条件；水稻也是如此，它是季风地区的主要农作物。

    My classmates talked about the winter camp. Everyone was happy except (除……之外) me. I didn't ____to go skiing (滑雪) at all. I wanted to stay at home but my parents asked me to go.

    When arriving at the camp our coach (教练) asked us to ski I thought I skied ____

than others but I still didn't do a good job. Ha, Ha! behind me，someone started ____

 I looked back ____who was laughing at me. To my surprise, I saw a girl. She did as ____as me. "I thought I'd be bad at this, but it seems ____than I expected!" she said.

    The next day I didn't want ____ skiing. But my coach chose me to be the first one to ski down the slope (斜坡).This time I ____I was flying and it was wonderful. After that I wasn't afraid anymore. And I didn't ____what other people thought of me. That day my coach said I skied the most beautifully of all.

    From this I learned that we should try our best ____every challenge (挑战).