利用氢氧化物沉淀分离,要严格控制溶液的pH值,下述()不能达到这一目的。
A.氨水法
B.H2SO4法
C.ZnO悬浊液法
D.有机碱法
参考答案:B
Because of the bad weather, my mother ____ and lay in bed. She ______ for a week.
A.has been ill; was ill
B.fell ill; has fallen ill
C.fell ill; has been ill
D.fell ill; is ill
模块结构中的基本符号○→表示
A.调用
B.转接
C.控制
D.数据