Question

what is unique about the sea snail that lives among the man - of - wars tentacles?
it produces pearls
it uses jellyfish venom for defense
it feeds on plankton
it glows in the dark

Explanation:

The sea snail that lives among the Man - of - War's tentacles is unique because it uses jellyfish venom for defense. The Man - of - War (a type of jellyfish) has venomous tentacles. This sea snail can incorporate or use this venom for its own protection against predators. Producing pearls is more commonly associated with certain oysters. Many marine organisms feed on plankton, so that is not a unique trait for this specific sea snail. While some marine organisms can glow in the dark (bioluminescence), that is not the unique trait related to its association with the Man - of - War's tentacles.

Answer:

It uses jellyfish venom for defense.