题目

For an increasing number of students at American universities, old is suddenly in. The reason is obvious: The graying of America means jobs. Coupled with the aging of the baby-boom （生育高峰） generation, a long life span means that the nation’s elderly population is sure to increase greatly over the next 50 years. By 2050, 25 percent of all Americans will be older than 65, up from 14 percent in 1995. The change brings big problems for government and society, of course. But it also creates career opportunities in medicine and health professions, and in law and business as well. “In 下列各组括号内，除杂质的方法或试剂错误的是    (    ) A．CuCl2溶液中混有CuSO4（BaCl2溶液） B．H2中混有CO(灼热的CuO) C．NaCl溶液中混有泥沙（过滤） D．CaCl2中混有CaCO3（稀盐酸）