Question

what role do jellyfish play in the ocean ecosystem?
they are top predators that eat large fish
they help control plankton populations and provide food for larger animals
they build coral reefs
they produce oxygen for other marine life

Explanation:

Jellyfish consume plankton, which helps regulate plankton numbers. Also, they are prey for larger marine animals like sea turtles. They are not top - predators (many larger animals eat them), do not build coral reefs (coral polyps do that), and do not produce significant oxygen (phytoplankton and plants do that).

Answer:

They help control plankton populations and provide food for larger animals