What Is the Explanation for the Rugged Mountain and Valley

What is the explanation for the rugged mountain and valley topography of the Basin and Range, some 1600 km inland of a plate boundary?

A) Recent terrane accretion moved the coastline westwards from the Colorado- Utah border as the ranges formed.
B) Doubling of the crustal thickness in the past few million years has occurred due to intense thrusting and folding inboard of the San Andreas Fault.
C) A series of multiple subduction zones were all active and closed up about the same time.
D) Low density hot mantle rock has upwelled to hold up ordinary crust to greater than normal elevations.