TOEFL Listening: ETS-TOEFL听力机经 - 2L95D750GOI1Z1GPP$

Why does the professor discuss trade-off theory? A. To emphasize the mutual benefits for coral and zooxanthellae B. To illustrate why coral that recover from bleaching can suffer lasting effects C. To explain changes that occur in corals that are resistant to high temperatures D. To clarify why bleaching events are worse in some places than in others