Which radio call-in plan is the most prudent?

A
The designated responsible person must be instructed to call the Coast Guard search and rescue authorities immediately if your call does not come in on schedule.
B
There must be a designated responsible person available at all times to receive your call.
C
There must be a designated responsible person who knows they are expecting your call at a certain time.
D
Two responsible persons should be designated so that one can relieve the other as necessary.
E