单项选择题

Normal pool elevation is the height in feet of the section of river above a dam. This height is measured from（）.

A.low steel on the Huey P. Long Bridge
B.mean sea level
C.the local water table
D.the minimum dam control level

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单项选择题

Most drill ships and barges have a walled opening below the derrick，open to the water’s surface and through which various drilling tools can pass down to the sea floor called a （）.

A.moon pool
B.spider deck opening
C.pontoon
D.keyway

单项选择题

Most covered lifeboats will right themselves after capsizing if the（）.

A.lower ballast tanks are filled with water
B.sea anchor is deployed to windward
C.fuel tanks are not less than half full
D.passengers are strapped to their seats