The author believes that in the later part of the 19th century, Chinese immigrants received

A．it caused a severe local earthquake in the past.
B．it pushes older rocks on the top of younger rocks.
C．it has three segments and covers a relatively large area.
D．it was hidden beneath California's largest city.

A．it tells people there will be an earthquake in the near future.
B．it changes the official earthquake prediction for the area.
C．it makes it possible for scientists to calculate the magnitude.
D．it proves scientists' long-time suspicion about hidden faults.