option A&B have word 'equivalent' which calls for concision issue....
also where ever there is a comparision ,we can straightaway reject the option having equivalent(personal experience).
pls explain y C is wrong.
Baten80 had a nice explanation for C in an earlier discussion of the same problem; "equivalent" and "equal" modify uncountable nouns, while "as many as" modifies countable nouns.
In this problem, population is countable, so "as many as" must be used.
Indeed "equal" sounds alright, and I'm sure I use it to modify countable nouns in my own speech; however, it is not grammatically correct.
I hope this helps. Please don't hesitate to correct me if I'm wrong. Thanks! http://gmatclub.com/forum/according-to-a-study-by-the-carnegie-foundation-for-the-81568.html
A few kudos won't hurt.