Question

what benefit do zooxanthellae get from their mutualistic relationship with corals?
oxygen
lower ph
color
sugars from photosynthesis
carbon dioxide

Explanation:

Corals are animals that have a mutualistic relationship with zooxanthellae (algae). Corals provide a protected environment and the compounds needed for photosynthesis to zooxanthellae. In return, zooxanthellae produce oxygen and sugars through photosynthesis. The sugars are used by the corals for energy. Zooxanthellae get oxygen from their own photosynthetic process, not from corals. Lower pH is not a benefit provided by corals to zooxanthellae. Color is not a resource for zooxanthellae. Corals do not provide sugars from photosynthesis to zooxanthellae (zooxanthellae do photosynthesis themselves), but they do provide carbon - dioxide which is a raw material for zooxanthellae's photosynthesis.

Answer:

E. carbon dioxide