单项选择题
The best estimate of the wind direction at sea level can be obtained from observing the direction of the（）.
A.cloud movement B.vessel heading C.waves D.swells
单项选择题 Steam smoke will occur when（）.
单项选择题 RYUKYU S TO SE 6 BEC 4－5.ISOL SHWRS.SEA 3 M BEC 2 M.SWELL SE 3－4M.This description is likely to be under the heading of（）.
单项选择题 Periodic publications notifying changes in，or additions to，previously published navigational data are（）.
