单选题If the buoyant force on a ship’s hull is equal to the displacement tonnage，the ship will（）.A require ballastB be down by the headC sinkD float

Which statement is TRUE concerning buoyant work vests aboard tankers ________．

A.They may be worn while working on deck but not while working over the side

B.They must be used only under supervision of a designated ship's officer

C.They will be accepted for up to 10% of the required life preservers

D.They may be worn during drills

We have stayed at Shanghai port for a long timeThe fouling on the ship’s hull greatly increases her _____.

A.power

B.speed

C.resistance

D.thrust force

For a vessel inclined by the wind, multiplying the buoyant force by the horizontal distance between the lines of action of the buoyant and gravity forces gives the ______.

A.righting moment

B.longitudinal moment

C.transverse moment

D.vertical moment

All the following is true except that ______．

A.in many places a counter current flows in opposition to the main current close to the bank

B.current can vary with depth of water and large deep draught ships can experience different current effects at differing parts of the hull tend to turn to the wind

C.as speed is reduced，the increased proportion of the ship's vector which is attributable to current will set the ship close to obstructions

D.when close to the berth in a head current，there is a danger that flow inshore of the ship becomes restricted and the ship is subject to interactive forces