a student hypothesized that pillar coral eat and digest zooxanthellae for energy. which observation would cause the student to change this hypothesis? a. the zooxanthellae in a pillar coral's body are alive. b. pillar coral are a type of coral that needs sunlight to survive. c. the pillar coral are an important part of many coral reefs. d. zooxanthellae are a type of phytoplankton found in the ocean.