看汉字，写拼音。
____
牙
毛
巾
俄罗斯拥有世界上最深的湖泊（ ）
v表示速度，t表示时间，s表示路程．
s=____，v=____，t=____
下列有关化学实验的说法正确的是( )
There is a common saying in China________nothing in the world is difficult for one who sets his mind on it.
