新prep1-233 (GWD-12-Q32)，请教

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. because of erosion, prehistoric glacier movement, and ancient, gold-bearing riverbeds thrust to the surface by volcanic activity put gold literally within reach for

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. owing 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

答案是e，错b，此题做的有点混乱，没有思路了，请教各个选项的错误点，多谢

A because of 后不接句子

B\C, and putting 没有平行对应点

D since没有接句子

A、B、C皆错在句子重心问题  “ Prospecting for gold during the California gold rush was a relatively easy task” 的原因不是"erosion, prehistoric glacier movement, and ancient, gold-bearing riverbeds "这三个名词  而应该是“erosion, prehistoric glacier movement, and ancient, gold-bearing riverbeds put gold literally within reach of anybody with a pan or shovel.”这句话

只有E完整地表述了原因

补充下，从各个字典看只有within reach of sb这个搭配.这里reach的意思是extent to which a hand, etc can be stretched out.

since erosion, prehistoric glacier movement, and ancient, gold-bearing riverbeds thrust to the surface by volcanic activity put gold literally within reach of anybody with a pan or shovel.

结构应该是： since A, B, and C put gold literally within the reach of ...

                          A erosion, B prehistoric glacier movement,

                          C ancient, gold-bearing riverbeds(that) thrust to the surface by volcanic activity