单项选择题
A.only one high and one low water occur during a lunar day B.the high tide is higher and the low tide is lower than usual C.the high tide and low tide are exactly six hours apart D.two high tides occur during a lunar day
A strong back refers to a（）.A.bar securing a cargo port...
单项选择题A strong back refers to a（）.
A.bar securing a cargo port B.centerline vertical bulkhead C.deep beam D.spanner stay
A stretch where the channel changes from one side of th...
单项选择题A stretch where the channel changes from one side of theriver to the other is called a（）.
A.crossing B.transit C.transfer D.passing
A stream of water immediately surrounding a moving vess...
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（）.
A.directional current B.forward current C.propeller current D.wake current
