單項選擇題

All echo-sounders can measure the（）.

A.actual depth of water
B.actual depth of water below keel
C.average depth from waterline to hard bottom
D.average depth of water to soft bottom

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單項選擇題

All electrical appliances aboard a vessel should be grounded to（）.

A.prevent them from falling when the vessel rolls
B.protect personnel from electrical shock
C.increase their operating efficiency
D.prevent unauthorized personnal from operating them

單項選擇題

All entries in logbook,（）made,must not be erased or amended.

A.once
B.whether
C.previous
D.just