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

A．horizontal faults are more dangerous than vertical faults
B．Vertical faults are more dangerous than horizontal faults
C．Earthquakes occur only around fault areas
D．California will break into pieces by an eventual earthquake

A．defense planning after the Cold War
B．defense planners' problems
C．small conflicts in the world
D．potential warfare