What is "seismic monitoring and how is related to "Snell's Law?"
Please help :)

Explanation:

Seismic is a technique or method , the routine, analysis and activity of seisomograms to detect and locate underground nuclear explosions of a region. Seismic waves are measured by an instrument called seismometers.

Snell's law is the relationship between the angle of incidence and refraction of a wave and indices of the refraction of two media.

Snell's law describe how seismic ray paths bend as they travel from one medium to another. When the waves refracted 90°, it travel faster through the medium.

i think that d. wind is the answer.   i missed the question when i answered a. currents.