B is the answer to this question. The answer is based on the shown diagram. There are some people who may get confused with what a bedrock actually is. This is the type of solid rock that is usually found beneath the soil. There are some areas in the world wherein the bedrock may be more visible.
The granite bedrock is formed because of the cooling of magma. Once it solidifies, it becomes bedrock. This is known to extend far beyond the surface of the earth so it will be hard to actually measure its length unless there are actual numbers that are given that can be used for the computation.