TOEFL Listening: TPO-TOEFL听力TPO - 52M1FFV2L3X2VPSFR$

What does the professor imply about the term "symbiosis"? A. It is often used with too narrow a meaning. B. It is used incorrectly in the students' textbook. C. The original definition is difficult to understand. D. It is applied only to organisms of the same species.