氧化铝适于分离哪类成分（）
A.碱性成分
B.酸性成分
C.苷类
D.中性成分
E.弱碱性成分
参考答案：A
Shirley _____ a book about China last year, but I don't know whether she has finished it.
A．has written
B．wrote
C．had written
D．was writing
冷柱头进样的缺点有（）。
A.进样体积小
B.操作复杂
C.柱子寿命短
D.分析精度差
