Similarities between oil and gas sonic/seismic exploration and the use of seismic waves to find out about earth’s interior? differences?

Both oil and gas exploration involves the use of seismology. Seismic waves are generated from the surface and are bounced back from the crust interior. The returning waves are picked up by sensors and analyzed. The densities of the two determine how the wave is reflected and their depth can also be determined.

The different properties, especially density, between the two differentiate how the fossils fuels reflect the seismic wave. Oil is denser than gas hence low-frequency waves are reflected more by the oil than the gas. The same principle of S and P waves is applied – P waves pass through the entire rock layers of the earth whole S- waves cannot pass through fluids (such as mantle).  

the answer would be b).