单项选择题 A vessel，which is unable to maneuver due to some exceptional circumstance，shall exhibit （）.

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（）.