单项选择题 A stretch where the channel changes from one side of theriver to the other is called a（）.

单项选择题 A stream of water immediately surrounding a moving vessel’s hull，flowing in the same direction as the vessel is known as（）.

单项选择题 A situation has occurred where it becomes necessary for you to be towed. What action should be taken to prevent your vessel from yawing?（）.