单项选择题
A.avoid crossing the channel if it impedes another vessel navigating in the channel
B.not overtake any vessels within the channel
C.keep as close as possible to the edge of the channel on her port side
D.anchor only in the middle of the channel
单项选择题 A vessel aground at night is required to show two red lights in a vertical line as well as （）.
单项选择题 A vessel（）when underway shall so far as possible，keep out of the way of a vessel not under command.
单项选择题 A vessel（）a crossing vessel，shall not normally enter a separation zone or cross a separation line.