A：Laugh is good medicine.
B：Always take good medicine.
C：Medicine can make you laugh.
配制2000g生理盐水（溶质质量分数为0.9%），需要称取NaCl的质量为( )
—As we know it's difficult to live in a foreign country.
—________________ if you can't understand the language there.
某钢铁厂用100t含氧化铁80%的赤铁矿炼铁，计算理论上可冶炼出铁的质量．
