—The hazy weather has ________ for almost a week in North China.—Yes, and the government has tried to solve it.
It ____ ____ ____ difficult to get drinking water here.
秦始皇统一六国后,采取了许多措施,其中,对促进我国各地经济文化交流有巨大贡献的措施是( )
剪刀的刀口 斜面
镊子 省力杠杆
旗杆顶部的轮子 费力杠杆
钥匙 轮轴
小杆秤 滑轮