Questions 15 to 17 are based on the
following passage. At the end of the passage, you will be given 15 seconds to
answer the questions. Now listen to the
passage.
What did the study of seismic vibrations help geologists learn more about
A．When the Earth was formed. B．The composition of the Earth’s interior. C．Why lava is hot. D．How often a volcano is likely to erupt.