Final answer:
Louie is the unofficial leader among the three castaways because he is physically strong, creative, and has a clear mind.
Step-by-step explanation:
Among the three castaways, Louie is the unofficial leader because he possesses all the qualities listed in options A, B, and C. He is the strongest one physically, demonstrated by his ability to escape strafing from the Japanese plane. He is also very creative, as seen when he made a hook out of his lieutenant's pin. Additionally, he displays great lucidness of mind, as shown by his ability to remember his family's tall, yellow dog from his toddler days.