中华民族创造了辉煌灿烂的文化，突出表现在（  ）

①我们的祖国山河壮丽，江山如画                              ②汉字是世界上使用世界最长的文字之一

③书法，绘画，歌剧等艺术成就璀璨夺目                  ④“四大发明”等科技成绩享誉世界

世界上降水最丰富的地区        （    ）

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____.

    Before you go to another country it is a great help if you know the language and some of the customs of the country.
    When people meet each other for the first time in Britain, they say “How do you do?” and shake hands. Usually they do not shake hands when they just meet or say goodbye. But they shake hands after they haven't met for a long time or when they will be away from each other for a long time.
    Last year a group of German students went to England for a holiday. Their teacher told them that the English people hardly shake hands. So when they met their English friends at the station, they kept their hands behind their backs. The English students had learned that the Germans shake hands as often as possible, so they put their hands in front and got ready to shake hands with them. It made both of them laugh.

已知反应：①SO₃+H₂O═H₂SO₄②Cl₂+H₂O═HCl+HClO

③2F₂+2H₂O═4HF+O₂↑        ④2Na+2H₂O═2NaOH+H₂↑

⑤SiO₂+2NaOH═Na₂SiO₃+H₂O