用化学用语填空．

①2个氮原子____；

②铁离子____；

③地壳中含量最多的元素____；

④氢氧化铝中铝元素显+3价____．

《新全球史》认为，二战后美国的政治家和商业领袖想建立一套符合自己利益的国际贸易体系。在他们的推动下，取消了阻碍跨国自由贸易的限制性贸易惯例，最终推动建立了无限制全球贸易工具——关贸总协定。这一工具（    ）

一次函数y=-x的图象平分（　　）

根据短文内容从方框中选择恰当的单词填空，使短文完整、通顺。有的需要变换形式，每词限用一次。

lose,   quick,   pity,   age,   gold,   player,   begin,   win

    Lin Dan is a world-famous badminton (羽毛球)player. He was born on 14th October 1983 in China. He____playing badminton when he was five years old. He played quite well and became the world's No.1 player at the____of 19. He helped China ____ the Thomas Cup and the Sudirman Cup. He ____in the men's singles final at the 2006 Asian Games in Doha. It was a great ____. But two years later, he made up for(弥补)the loss by winning the____medal at the Beijing Olympics. Lin Dan is a left-handed player and he is very____. He is the first badminton____to win a career grand slam(大满贯)：Olympic Games，World Championships，Asian Games，All England Open and all the top world events(比赛项目).

A～G是几种烃的分子球棍模型，据此回答下列问题：