awesome explanation by
e-gmat (always clear).
lets apply our 3-step process to solve this one.
Meaning: This sentence shows a cause and effect.
Effect = prospecting for gold was easy during gold rush
Cause = This happened because the factors below caused the gold to come within reach of people
Erosion
Glacier movement
Riverbeds
Error Analysis:
Error 1: SV - Must Exist
There are two clauses in this sentence:
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.
SV Pair in Clause 1 = Prospecting – was
SV Pair in Clause 2 = no subject – put
Here is why:
Clause 2 (simplified form) = Because of A, B, and C put gold...The presence of "of" after because implies that A, B, and C cannot be the subject for the verb - put because these elements fall in prepositional phrase. This can be corrected by any of the following edits:
Because A, B, and C put gold...
Because of A, B, and C gold was put...(Change active voice to passive voice).
My preference is the first edit since it is more precise than the second edit.
Error 2: reach for is not idiomatic usage. It should be reach of.
Lets simplify the idiom usage:
The can is in the reach of the child.
The can is in the reach for the child.
Clearly reach of is better than reach for.
Note that "thrust to the surface..." is a verb-ed modifier that modifies the preceding noun - riverbeds.
POE:
Choice 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
Error 1: Changes intended meaning
This choice changes the list. The list per this choice is as follows:
Effect = prospecting for gold was easy during gold rush
Cause = There is a list of reasons:
Erosion
Glacier movement
volcanic activity
that thrust riverbeds to the surface
and putting gold within reach of people
This choice now implies that erosion, glacier movement and volcanic activity - 3 factors thrust riverbeds to the surface. This is different from the intended meaning - volcanic activity thrust riverbeds to the surface.
Furthermore, this choice implies that prospecting for gold was easy because riverbeds were thrust to the surface and gold was put within the reach. This is again not the intended meaning - prospecting for gold was easy because gold was within reach of people because of three factors - erosion, glaciers, and riverbeds.
Error 2 - List is not grammatically parallel.
Because of
A, B, and C that did something
putting...
Choice 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
This choice also has similar errors as Choice B does.
Additionally, as you indicated "had thrust" is incorrect. It should be simple past tense.
As with choice B, even if we replaced putting with put, it will still contain both errors.
Choice D: since erosion, prehistoric glacier movement, and volcanic activity that thrust ancient, gold-bearing riverbeds to the surface, putting gold literally within reach for
Error 1: Subject Verb Must Exist
The subject - erosion, glacier movement, and volcanic activity has no verb
Error 2: Changes intended meaning.
Notice again that the list has been changed. The third element is now volcanic activity instead of riverbeds.
Error 3: reach for is idiomatically incorrect
Choice E: Correct answer