读一读，把错误的地方改正过来。

①我们要珍贵别人的劳动成果。

②这次活动，小明和全班同学都参加了。

③我穿上衣服和帽子出去玩。

一名质量为60kg训练有素的武警战士（视为质点）在楼顶通过一条长绳由静止开始下滑，到地面最短时间t=2.4s．已知该武警战士落地的速度不能大于v=6m/s，做匀减速直线运动时可以产生的最大加速度大小为a=5m/s²，长绳的下端恰好着地，当地的重力加速度g=10m/s²．求：

在物理学习的过程中，经常会用到一些科学研究方法．下列事例中运用相同科学研究方法的是（　　）

（1）用水流比作电流              

（2）探究同一直线上二力的合成

（3）探究液体内部压强规律        

（4）用总电阻替代两个串联的电阻．

                                     C

    People call the Winter Olympics the White Olympics. At this time, they publish(发行) many stamps to mark(标志) the great games. The first stamps came out on January 25th, 1932 in the United States for the 3rd White Olympics. From then on, publishing stamps during the White Olympics became a rule.

    During the 4th Winter Olympics, people published a group of stamps in November 1936. They drew five rings of Olympics. It was the first time that the rings appeared(出现) on the stamps of the White Olympics.

    In the 1950s，the stamps of this kind became more colorful. When the White Olympics came, the host countries as well as non-host countries published stamps to mark those games. China also published four stamps in February 1980 when the Chinese sportsmen began to take part in the White Olympics.

    In Asia, Japan was the only country to hold the White Olympics. They sold 14,500 million stamps during the Olympics.

    People drew different kinds of sports on these small stamps, and they enjoyed the wonderful sports and some famous players.

某天，六年级一班出勤47人，有3人请假，这天的出勤率是____．