The correct answer is - A. San Andreas Fault.
The San Andreas Fault is stretching alongside the western coast of the United States. It is a result of a divergent plate boundary, where the westernmost part of the country is slowly moving away from the North American mainland.
As it moves more and more, this part will come to a situation where the crust will be much thinner and easier to crack under the high pressure, temperatures, and magma from the mantle layer bellow. As this stats to happen, the region, already pretty active geologically, will become even more active geologically, and the stress on the crust will be result in very often and strong earthquakes.
