Prospecting for gold during the California Gold rush was a relatively easy task, because of erosion, prehistoric glacier movement, and ancient , gold-bearing riverbeds thrust to the surface by volcanic activity put gold literally within reach for anybody with a pan or shovel.
A. Same
B. because of erosion, prehistoric glacier movement, and volcanic activity that thrust ancient, gold-bearing riverbeds to the surface, and putting gold literally within reach of
C. owning to erosion, prehistoric glacier movement, and volcanic activity that had thrust ancient, gold-bearing riverbeds to the surface, and putting gold literally within reach of
D. since erosion, prehistoric glacier movement, and volcanic activity that thrust ancient, gold-bearing riverbeds to the surface, putting gold literally within reach for
E. since erosion, prehistoric glacier movement, and ancient gold-bearing riverbeds thrust to the surface by volcanic activity put gold literally within reach of
I originally chose A, but E is the correct answer. Is it because E is more passive? Also, is within reach for idiomatic? It doesn't sound right, so I probably shouldn't have selected A on that alone.