Please answer the following question: Mary is studying the seismic waves of a recent earthquake from 2 locations around its focus. She notes at point A the waves are easily detectable. at point B the waves are unable to be read at all, as if they just stopped. Given Mary decides to check the readings for two other locations, points C and D, and notices the waves at D are slower, will the areas underground at points C and D be made of the same materials or different materials?
Answer:
different