清洗龙虾的“洗虾粉”中含有的亚硫酸钠(Na2SO3)可能对人体的健康产生危害。Na2SO3中S元素的化合价为( )
A _______ to a problem is a way of dealing with it so that the difficulty is solved.
计算(2a3)2的结果是( )