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

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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

单项选择题

Mean low water is the average height of（）.

A.the surface of the sea
B.high waters and low waters
C.all low waters
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In the Sargasso Sea there are large quantities of seaweed and no well defined currents. This area is located in the（）.

A.Central North Atlantic Ocean
B.Caribbean Sea
C.Western North Pacific Ocean
D.area off the west coast of South America