单项选择题
A.an anchor light
B.sidelights and a sternlight
C.three lights in a vertical line，the highest and lowest being red，and the middle being white
D.None of the above
单项选择题 A vessel crossing a river on the Western Rivers has the right of way over（）.
单项选择题 A vessel continually lists to one side and has a normal rolling period. Which statement is TRUE?（）.
单项选择题 A vessel constrained by her draught may，in addition to the lights prescribed for power-driven vessels in Rule 23，exhibit where they can best be seen（）or a cylinder.