1st bold face: an objection to the alternative plan proposed (plan to replace property taxes with retail taxes)
2nd bold face: the second bolded face offers mitigating factors that weaken the objection to the alternative plan=> supports the alternative plan
A is a summarization of the above.
D doesnt cut it as the argument doesnt refute the objection. notice it says "The critics are correct on this point". it doesnt refute the objection, it just weakens the objection by showing some mitigating factors.
(refute is different from weaken. refute= something is fdefinitely false, weaken=something is not foolproof/can be attacked)