Explanation:

Detritivores are organisms that feed on and break down dead plant or animal matter, returning essential nutrients to the ecosystem.

Earthworms: They are detritivores. They feed on organic matter like dead leaves and break them down, enriching the soil in the process.

Jellyfish: They are carnivores that feed on small planktonic animals.

Millipedes: They are detritivores and primarily feed on decaying leaves and other dead plant matter.

Seahorses: They are carnivores and feed on small crustaceans.

Woodlice: They are detritivores. They feed on decaying leaf and plant matter.

Hence, the correct organisms that are detritivores among the given options are Earthworms, Millipedes, and Woodlice.