单项选择题
A.on a collision course
B.the vessels will pass within one mile
C.it becomes apparent to her that the give-way vessel is not taking appropriate action
D.the relative speed of the vessels indicates collision in less than six minutes
单项选择题 A marker pole，with a horseshoe buoy and a sea anchor attached，should be used to （）.
单项选择题 （）objects are those which stand out clearly from the background or other objects and are easily identifiable from a few miles offshore in normal visibility．
单项选择题 （）day，pilot flag should be displayed from main mast．