The color of the signal flare sent up by a submarine about to surface due to an emergency condition within the submarine is（）.

A.two years
B.three years
C.four years
D.five years

A.annually by the owner，with a letter submitted six months before expiration
B.only once every five years，with a letter submitted six months before expiration
C.and the entire plan resubmitted for approval once every five years，six months before expiration
D.annually by the owner，with a letter submitted to the Coast Guard within one month of the anniversary date of the plan approval

A.opening dead spaces to check for heat or fire
B.evacuation of the vessel
C.sounding the "all clear" signal
D.operation of the emergency generator