①点燃蜡烛，紧贴烛芯将火柴梗放入火焰中约1 秒后取出

②在火焰上方罩一个冷而干燥的小烧杯；

③用火柴去点白烟；

④切下一块石蜡，放入水中；

⑤熄灭蜡烛；

⑥迅速倒转烧杯，加入澄清石灰水，振荡．

请回答以下问题：

我们应怎样对待竞争？ 

Mr Green had a little boy. Every day had work he came home and played with his son.
One night ,while Mr Green was at work, he 1 that he had extra work to do for the evening ,and that he wouldn’t be able to play with his son.2he wanted to give the boy something to keep him3. So , looking around his office , he saw a 4with a large map of the world on the cover(封面). He got an 5 He removed the map , tore(撕) it up into small pieces and put all the pieces in his coat pocket.
When he got home , the little boy came running to him and was ready to play. Mr Green6that he had extra work to do and couldn’t play at the moment . Then he 7 all the pieces of the map and put them on the table . He said to the  boy,”8” was a map of the world, and  9th time you put it back together, my extra work will be finished, and we can 10”. Surely, this would keep the child busy for   11  , he thought.
About half an hour later the boy came to Mr Green and said,” Okay, it’s  12 . Can we play now?”
Mr Green said ,“That’s amazing!13did you do that?” The boy said, “It was14. On the back of the page was a picture of a man . When I put the man together the whole world fell into place.”

某同学看到一只鸟落在树枝上的P处(如图所示)，树枝在10 s内上下振动了6次。鸟飞走后，他把50 g的砝码挂在P处，发现树枝在10 s内上下振动了12次。将50 g的砝码换成500 g的砝码后，他发现树枝在15 s内上下振动了6次。你估计鸟的质量最接近____ g。

读某河水系略图，完成各题。