What is the best description of the relationship between zooxanthellae and coral polyps?

Question

1) it is a predator-prey relationship because the polyps feed on the zooxanthellae
2)it is a parasitic relationship in which the zooxanthellae burrow themselves within the tissue of the polyp and take nutrients from them
3)it is a symbiotic relationship in which they both depend on one another for survival
4)the zooxanthellae are a sign of distress on the reef-they invade the polyps and cause coral bleaching

Answer 1

The best description of the relationship between zooxanthellae and coral polyps is:

3) it is a symbiotic relationship in which they both depend on one another for survival.

In this mutualistic relationship, zooxanthellae are photosynthetic algae that live within the tissues of coral polyps. The corals provide the zooxanthellae with a protected environment and the organic compounds they produce through photosynthesis, while the zooxanthellae help the corals by providing them with essential nutrients and aiding in the formation of calcium carbonate skeletons.