TOEFL Listening: ETS-TOEFL听力机经 - P7WTO3M4I4JW9HL4P$

What did the researchers discover about small soil pores? A. Small pores make the movement of water through soil difficult to trace. B. The number of small pores in the soil of a specific area is related to the number of hydrogen isotopes there. C. Trees receive less water from small pores than from large pores. D. Small pores retain water longer than previously thought.