At Present,an Earthquake Warning System Could Provide Up to a One

At present,an earthquake warning system could provide up to a one minute warning to regions far enough away from the epicentre of an earthquake.Such a warning system is based on the difference between

A) P-wave and S-wave velocities.
B) P wave and surface wave velocities.
C) radio wave and seismic wave velocities.
D) sound wave and seismic wave velocities.
E) ultrasonic wave and seismic wave velocities.