单项选择题
Currents are（）in rate and direction.
A.vary
B.variable
C.variably
D.variability
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相关考题
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单项选择题
Current refers to the（）.
A.vertical movement of the water
B.horizontal movement of the water
C.density changes in the water
D.None of the above -
单项选择题
A structure，usually made of stone，or cement pilings，which extends from the bank at approximately right angles to the current is called a（）.
A.dike
B.revetment
C.cutoff
D.crib -
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
