题目

阅读下面短文,在空白处填入1个适当的单词或括号内单词的正确形式。Learning how to choose a career is not only important for adults but also for students at college. People decide to have their careers 【1】 (change) simply because they dislike the job they 【2】 (current) have. They take on the jobs not because they like them but because they need to make a living. In this case, 【3】 (get) career guidance is very important. The first step in choosing a career 【4】 (be) understanding yourself. This will help you realize what you enjoy doing.The best way to do证明生石灰中既混有石英,又混有石灰石的正确方法是( )A．加入过量的盐酸,观察是否有气泡冒出B．加入过量的烧碱溶液,观察是否有固体溶解C．加热至高温,观察是否有气泡冒出,是否有硅酸钙生成D．先加过量的盐酸搅拌,观察是否有不溶物剩余及气泡出现;若有不溶物则滤出,投入到氢氧化钠溶液中看其是否溶解