质地均匀，外形规则的物体的重心在物体的____上．物体的重心越低，它越____．

The chemistry teacher demanded that the laboratory report _______ immediately after the experiment was done.

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).

学校为了调查学生在课外读物方面的支出情况，抽出了一个容量为的样本，其频率分布直方图如下图所示，其中支出在元的同学有人，则的值为    

向自行车胎打气时，适当情况下可多可少，这说明（）