连续回流提取法使用的仪器是
A．索氏提取器B．超声清洗器C．渗滤器D．旋转蒸发器E．以上都不是
参考答案：A
There are hundreds of visitors _____ in front of the Art Gallery to have a look at Van Gogh's paintings. [ ]
A. waited
B. to wait
C. waiting
D. wait
监事会由 * * 1人．监事若干人组成，监事会成员不少于( )人。
A．2
B．3
C．5
D．6
