Each emergency generator on a mobile offshore drilling unit，when tested，must be run under a full load for at least（）.

A.release the towline in an emergency
B.help the helmsman steer
C.look for food and water
D.check the water level in the bilge

A.minimizing the affects of unintentional flooding
B.fire on board
C.rescuing an individual from the water
D.emergency towing

A.annually
B.once every two years
C.once every four years
D.once every five years