薄层色谱法测苯甲酸、山梨酸时．样品提取中，选用( )起脱水作用
A．无水氯化钙
B．无水浓硫酸
C．无水硫酸钙
D．无水硫酸钠
参考答案：D
I'm ______ my book that I don't notice him stand beside me. [ ]
A. very absorbing
B. very absorbed in
C. so absorbed in
D. as absorbed in
刺激牙龈增生的是（）
A.四环素
B.吲哚美辛
C.甲硝唑
D.苯妥英钠
E.氯已定
