两个相似三角形的面积比是9∶16，则这两个三角形的相似比是 [ ]
A．9∶16
B．3∶4
C．9∶4
D．3∶16
答案：B
More and more people in Shanghai are able to talk and write _____ English these days. [ ]
A. for
B. with
C. in
D. to
无线通信导频单工方式下，在150MHZ频段，收发频率间隔一般为（）
A.5.7M
B.10M
C.45M
