Breeding Bird Survey

Dean Jones wrote:Dear Friends,

I was having problems in answering the following question.

Organized in 1966 by the Fish and Wildlife Service, the Breeding Bird Survey uses annual roadside counts along established routes for monitoring of population changes of as many as, or of more than 250 bird species,including 180 songbirds.
(A) for monitoring of population changes of as many as, or of
(B) to monitor population changes of as many, or
(C) to monitor changes in the populations of
(D) that monitors population changes of
(E) that monitors changes in populations of as many as, or

Prep phrase "for monitoring of population changes of as many as, or of..." indicates purpose of THE SURVEY. Therefore, IMO its always better to show the purpose with Preposition TO (ie TO MONITOR is prefered over FOR MONITORING).

B - idiom AS MANY is incomplete (We need AS MANY AS)

D/E - THAT MONITORS

Lets analyze it further: "the Breeding Bird Survey uses annual roadside counts..that MONITORS..". Note here, the VERB is MONITORS. There is only singular subject coming before MONITORS that is "SURVEY". It means D/E says "Survey uses.. counts.. that monitors..", meaning survey is monitoring changes in populations of species. This meaning is very different from original meaning of the sentence that says "Survey uses counts with a purpose to monitor changes in population".

Moreover, I always prefer "changes in populations" to "population changes".

IMO C

Is population's' correct here?

Please help!