As used in the first sentence of the fourth paragraph, the word "essentially" means_____.

A．the New Madrid fault in Missouri
B．the San Andreas and the New Madrid faults
C．the causes of faults
D．current scientific knowledge about faults

A．it is probably as dangerous to live in Missouri as in California
B．the New Madrid fault will eventually develop a mountain range in Missouri
C．California will become an island in future
D．A big earthquake will occur to California soon