Certain pesticides can become ineffective if used repeatedly in the same place; one reason is suggested by the finding that there are much larger populations of presticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.
(A) Same
(B) If used repeatedly in the same place, one reason that certain pesticides can become ineffective is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

(C) If used repeatedly in the same place, one reason that certain pesticides can become ineffective is suggested by the finding that much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than those that are free of such chemicals.

(D) The finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals in suggestive of one reason, if used repeatedly in the same place, certain pesticides can become ineffective.

(E) THe finding of much larger populations of pesticides-degrading microbes in soils with a relatively long historyof pesticide use than in those that are free of such chemicals suggests one reason certain pesticides can become ineffective if used repeatedly in the same place.

The correct answer is (A). Please help understand why (A) is the correct one. Specifically in terms of uage of ';' in the sentences.

Thanks
GMAT 2007

A semi-colon can only be used correctly if both sentences are independent clauses - that is, each could be a stand-alone sentence exactly as written. Also, in the real world, the two sentences should be connected in some way (talking about the same thing). That bit won't get tested on the GMAT because they only give you one sentence, so there's no alternative answer choice to using a semi-colon when the two sentences shouldn't be connected (they can't give you another choice in which they do split it into two separate sentences).

In this case, the semi-colon is used correctly. For the other sentences, the issues don't revolve around semi-colon usage; you have to use other reasons to eliminate them. Let me know if you have questions about any of the specific errors in the other choices.

By the way, notice that the original sentence sounds a little bit awkward, even though it is grammatically and structurally correct. When the correct answer is A, it isn't unusual for that original sentence to sound a little funny - that's how they get us to pick something else, even though we read the correct sentence first. Just watch out for that!

Thanks for the explanation.

GMAT 2007