The article suggests that a solution to the problem

A．were welcomed with hospitality.
B．far outnumbered other minorities.
C．arrived mostly in the 1870s.
D．were met with obvious hostility.

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.