They can speak Chinese and .
A:British
B:India
C:German
D:Russia
As we know, his father is a very famous scientist in physics. But what you don't know is that he _______ as a farmer for five years.
物质的性质不仅决定了它的用途,还决定了它的保存方法.固体氢氧化钠具有以下性质:①有腐蚀性;②易吸收水蒸汽而潮解;③易溶于水,溶解时放出热量;④能与空气中的二氧化碳反应.实验室中固体氢氧化钠必须密封保存的主要原因是( )