一般而言，选择玻璃做载体，则液担比（）。
A.可大于1：100
B.可小于1：100
C.5：50
D.（5-30）：100
参考答案：B
12. Mr. White works with an import and export company, but he ______ for this industrial fair, since he is on leave.
A．has worked
B．works
C．has been working
D．is working
试述肾动脉狭窄的临床诊断线索。
ort and export company, but he ______ for this industrial fair, s
ince he is on leave.