TOEFL Listening: ETS-TOEFL听力机经 - 1_33D0D93Q885P_ZP$

What is the professor's opinion about the effect of global warming on methane hydrates? A. Methane hydrates could become more abundant sediments on the ocean floor. B. Methane hydrates could become more difficult to extract. C. Methane hydrates could disappear from the Earth except the Arctic. D. Methane hydrates could become dangerous even if humans do not try to extract them.