My Choice is B (still it looks little awkward to me)

A. "IT" which modifies the developments should be plural.
C. doesn't have any meaning (it says that the developments are not the new principle and also the word "the same one" is very confusing"
D. same problem like C
E. same problem like A (IT is wrong)

Answe is B...

follows the correct idiom is not x....but y....

D also has correct idiom but it shows absurdity.....

DROBULESH wrote:809. The proposed urban development zones do not represent a new principle; it was employed in “Operation Bootstrap” in Puerto Rico.
(A) do not represent a new principle; it
(B) represent not a new principle, but one that
(C) are not a new principle; the same one
(D) are not a new principle, but one that
(E) are not new in principle; it

a- it modify the principle correctly but we talk here that the proposed present a principle but it's not new one... so in A the sentence says that the urban zones not present not a new principle while on the second clause we say that this principle which was present in the urban development zones, is employed already...

the tip: understand the meaning of the sentence...

c,d,e out - the urban development zones are not a principle, they present a principle...

in answer A "it" can't refer "principle". "principle" is neither a subject nor an object for the pronoun "it" to refer in this sentence.

I still feel B is correct.

Can some expert comment please.