单项选择题
A.during the day，three balls in a vertical line
B.during the day，three shapes，the highest and lowest being balls and the middle being a diamond
C.when making way at night，two all-round red lights，sidelights，and a sternlight
D.when making way at night，masthead lights，sidelights，and a sternlight
单项选择题 A vessel which through some exceptional circumstance is unable to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel is called（）.
单项选择题 A vessel travelling down a narrow channel，especially if the draft is nearly equal to the depth of the water，may set off the nearer side. This effect is known as（）.
单项选择题 A vessel towing astern in an operation which severely restricts the towing vessel and her tow in their ability to change course shall，when making way，exhibit（）.