TOEFL Listening: ETS-TOEFL听力机经 - 39BUM14C4MP8311PP$

Why does the professor discuss refrigeration? A. To emphasize the expense of producing proteins from plant seeds B. To point out the cost-effectiveness of transporting seeds C. To illustrate the difficulty of preserving some vaccines made from seed proteins D. To emphasize the need for more high-tech laboratories for extracting plant proteins