What tectonic event in the western U.S. caused magmatism and deformation to move farther into the continent during the late Mesozoic and early Cenozoic Laramide Orogeny?

a. the continent overran a hot spot
b. the continent overran the East Pacific Rise
c. continental extension stretched the continent to twice its original width
d. an oceanic plate subducted at a low angle beneath the continent