题目

For many people,being on the job might just sound like a picnic compared to a day at home filled with housework,meals and childcare.Even for those with a happy family life,home can sometimes feel more taxing than work. In a new study,researchers at Penn State University found significantly and consistently lower levels of cortisol（皮质醇）released in response to stress,in a majority of subjects when they were at work compared to when they were at home.This was true for both men and women,and parents and people without children. Both men and women showed less stress at work.But wome在除杂质过程中要尽量除去杂质，那么加入的试剂必须过量，最后过量试剂用物理或化学方法除去。现要除去NaCl溶液中的CaCl2、Na2SO4，下列选用试剂和使用顺序正确的是A．Na2CO3、BaCl2、HCl B．BaCl2、Na2CO3、H2SO4C．BaCl2、Na2CO3、HCl D．Ba(NO3)2、Na2CO3、HCl