The conclusion of this argument is that the town councilors feel that bus fares should be raised. Why? Because these councilors feel that taxes should be used to benefit tax-payers, and some of the folks who benefit from the low fares are commuters (i.e. non-tax payers).
We're asked to find the answer choice that does NOT weaken the argument. Let's knock down the ones that do:
(A) weakens the argument by presenting a reason that raising the fares would HURT the tax-payers, not benefit them.
(B) provides a reason that the higher fares would increase costs.
(C) is strange because it sets up two new premises. Along with establishing that poor folks would be disadvantaged by the higher fares, we learn that the councilors feel that poor folks should be able to take advantage of city-services. With that new rule in place, removing the subsidy doesn't make sense. (C) provides a rather separate reason that the subsidies are problematic.
(D) is out of scope -- there's no mention of concern with what the voters feel.
(E) disrupts the argument by showing that commuters can pay taxes, thus the use of taxes to benefit them would make sense.