TOEFL Listening: ETS-TOEFL听力机经 - 31Q1G5HDVN3183W5P$

What are two advantages of using a hydrophone to measure hurricane intensity? A. They can transmit underwater sounds to airplanes. B. They can lower the cost of monitoring hurricanes. C. They can be set up before a hurricane reaches an area. D. They can be installed close to the surface of the ocean.