用酸性染料比色法测定生物碱类药物,有机溶剂萃取测定的有色物是:
A.生物碱盐B.指示剂C.离子对D.游离生物碱E.离子对和指示剂的混合物
参考答案:C
Her sister ____ a taxi driver. Now she works for a charity.
A.is
B.were used to being
C.is used to being
D.used to be
在工程测量中,根据工程的实际情况应如何确定平面坐标系统?