mmslf75 wrote:thanks ron !!

glad it helped.

mohish wrote:I read a recommendation somewhere (forget where) that 'since' on GMAT is used only to depict time (example: Since 1980). So, in light of this sentence looks like that recommendation is not correct.

Can some expert please confirm.

Also, even after reading this sentence multiple times, I am not getting the 'meaning' of E. Would be wonderful if someone can explain it.

yep, it looks like this "recommendation" is wrong-o.
btw, it's always a good idea to retain the sources of advice -- the more sweeping or general the advice, the more important it is to retain the source -- so that you can then check those sources for their reliability and authenticity.

regarding the meaning of the sentence, try this:
* replace "since" with "because"
* replace "erosion, prehistoric glacier movement, and ancient, gold-bearing riverbeds thrust to the surface by volcanic activity" with "these 3 things"
then you get
Prospecting for gold during the California gold rush was a relatively easy task, because these 3 things put gold literally within reach of anybody with a pan or shovel.
is that easier to understand?

Resp007 wrote:HI,
Is the following sentence correct?
Prospecting for gold during the California gold rush was a relatively easy task, because of erosion, prehistoric glacier movement, and ancient, gold-bearing riverbeds.

It doesn't contain any grammatical errors, but it doesn't make sense. You've removed the actual REASON why "prospecting was an easy task", so now it's a non sequitur.

Analogy:
Everything in my suitcase is all wet because the heat caused a bottle of hair spray to explode.
... ok, that makes sense.

Everything in my suitcase is all wet because of the heat.
... Huh? Nonsense.

Same deal here.

Also, whether "prehistoric glacier movement" or "prehistoric glacier movements" correct in the sentence above?

The gmat wouldn't test this difference.