Minnesota is the only one of the contiguous forty-eight states that still has a sizable wolf population. and
where this predator remains the archenemy of cattle and sheep.
(A) that still has a sizable wolf population, and where
(B) that still has a sizable wolf population, where
(C) that still has a sizable population of wolves, and where
(D) where the population of wolves is still sizable;
(E) where there is still a sizable population of wolves and where

Ron, can you pls shed more light of Singular Vs Plural construction here.... is use of HAS is okay...

if it says the only one of..., then it's singular.
if it says only one of... (without the), then it's plural.

read my last post on this thread for more about this issue.