The correct response is: The polyps get most of their food from the algae.
This relationship is often described in the context of coral reefs, where corals (which are polyps) have a symbiotic relationship with zooxanthellae, a type of algae. The algae perform photosynthesis and provide nutrients to the polyps, while the polyps provide the algae with a protected environment and the compounds they need for photosynthesis.