Prospecting for gold during the California gold rush

Prospecting for gold during the California gold blitz was a almost accessible task, because of erosion, aged berg movement, and ancient, gold-bearing riverbeds advance to the apparent by agitable action put gold actually aural ability for anybody with a pan or shovel. A. because of erosion, aged berg movement, and ancient, gold-bearing riverbeds advance to the apparent by agitable action put gold actually aural ability for B. because of erosion, aged berg movement, and agitable action that advance ancient, gold-bearing riverbeds to the surface, and putting gold actually aural ability of C. attributable to erosion, aged berg movement, and agitable action that had advance ancient, gold-bearing riverbeds to the surface, and putting gold actually aural ability of D. back erosion, aged berg movement, and agitable action that advance ancient, gold-bearing riverbeds to the surface, putting gold actually aural ability for E. back erosion, aged berg movement, and ancient, gold-bearing riverbeds advance to the apparent by agitable action put gold actually aural ability of Answer: E I alone A and D because I anticipation that "within ability of" is the actual argot NOT "...within ability for anybody..." ?? I am not abiding why we use back and not because?