a sound wave traveling downward with a speed of about 4,000 m/s suddenly slows to 1,500 m/s not far below…

a sound wave traveling downward with a speed of about 4,000 m/s suddenly slows to 1,500 m/s not far below the earths surface. what has the sound wave most likely encountered? a different kind of rock an underground lake an open cavity a pile of dinosaur bones
Answer
Answer:
B. an underground lake
Brief Explanation:
Sound travels slower in water (as in an underground lake) than in most rocks. The speed - decrease indicates a transition to a medium like water.