检测高速血流应选用()
A.高频超声
B.低频超声
C.与频率无关
D.大口径探头
E.以上都不是
参考答案:B
—Will Mr. Smith be here soon?
—I can't tell, let's go and ________ when the train arrives. [ ]
A. find out
B. look out
C. find
D. look
A.5A
B.5A
C.3.5A
D.3.5A