TOEFL Listening: ETS-TOEFL听力机经 - Y43H7SD4NRTE8MQ0P$

What does the professor imply about supplies of natural gas? A. Supplies might be larger than previously thought. B. Supplies may eventually be replaced by other fossil fuels. C. Supplies are being depleted more quickly than predicted. D. Supplies should not be used as a main source of energy.