单项选择题
A Doppler speed log indicates speed over ground（）.
A.at all times B.in the bottom return mode C.in the volume reverberation mode D.only when there is no current
单项选择题 A Doppler log in the volume reverberation mode indicates（）.
单项选择题 A Doppler log in the bottom return mode indicates the（）.
单项选择题 A deadhead is a(n)（）.
