using elimination IMO A
why not D? because it says "the second is the main point
used by the argument to show that the claim is false. "
the claim is not false. its true.

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)

Edited.

guess you can use the second bold face too to eliminate D. it never struck me when i attempted the question

Edited.

agree with you on the main point/conclusion being "implementing the plan will probably not reduce the money going to Aroca’s schools"

may be the OE considers the 2nd boldface as the conclusion because of " In consequence". am not too sure.

what is the source?

the post in the link below mentions the OA as D

https://www.beatthegmat.com/bold-face-ar ... 39179.html

Edited.

It seems to me that the right answer is A.