It seems like answer choice A would be correct, since Passage A is arguing for a flat tax while Passage B is arguing for a graduated tax. However, the author of Passage B does not argue that a flat tax is not progressive. Author B acknowledges the exempt amount on lines 48-50. Rather, Author B is arguing that a graduated tax is better than a flat tax, even though it is possible for both to be progressive.
Here is the evidence for answer choice B:
Author B says specifically on line 56 that the high-income earners are going to pay less under a flat tax, fulfilling his/her end of the disagreement.
In paragraph two, author A gives multiple reasons why a flat tax can be just as progressive as a graduated tax.
Line 17: "Not so" in response to a claim that the wealthy don't have to forfeit a bigger share of income under a flat tax Lines 22-26: a flat tax makes it difficult for the wealthy to evade taxes Line 27-30: high-income earners usually pay about as much tax under new flat-tax regimes as they would have paid under the previous codes.
Although author A doesn't state it explicitly, this gives us enough reason to say that he/she most likely disagrees over answer choice B.
