Suppose an Ocean Liner Sinks and the Passengers Become Stranded

Suppose an ocean liner sinks and the passengers become stranded on a lush tropical island.Which of the following is most likely to be most useful as money in the economy that develops among the survivors?  

A)  the life jackets they put on when leaving the ship 
B)  beads from the necklaces that were the party favours the night the ship sank 
C)  the coconuts growing on the island 
D)  the fish swimming around the island