TOEFL Listening: ETS-TOEFL听力机经 - 2353133KE4J1Y2DTP$

How do scientists make it possible to hear sounds from the deep sea? A. By eliminating all low-frequency sounds from undersea recordings B. By combining recordings made underwater with recordings made above the water surface C. By making a recording in which nothing can be heard, then speeding up the recording D. By using a seismometer to identify the sound's location, then placing a hydrophone there