在房缺或室缺中，当血流方向与声束垂直或接近垂直时，为什么即使有较大的分流也不能清楚地显示出分流频谱。

All of the following records are usually maintained by the watch-standing officers aboard a vessel except the（）.

A.deck logbook

B.official logbook

C.compass record book

D.chronometer error book