Questions 17 to 20 are based on the following passage. At the end of the passage, you will be given 20 seconds to answer the questions.
Now listen to the passage.
What can we infer from the talk
A．Powerful earthquakes usually occur after minor ones.
B．Modern facilities add to the danger of an earthquake.
C．Passing trucks are as dangerous as minor earthquakes.
D．There is a powerful earthquake occurring every two years.