TOEFL Listening: ETS-TOEFL听力机经 - 7JW98XMY1001E385P$

What does the professor imply about iron in the glacial pool that he discusses? A. It is present in unusually low amounts for a glacial pool. B. It helps prevent the water in the pool from melting the glacier. C. It allows bacteria to maintain a constant supply of sulfate in the pool. D. It combines with excess oxygen in the pool.