When we're asked to resolve a paradox or discrepancy, we need to establish three things:

1) What are the given premises?
2) What would the expected outcome be?
3) How does the actual outcome differ from the expected outcome?

In this case,
1) Given: the wealthiest 20% contribute more than 70% of tax revenue
2) Expected (Congressperson's position): the wealthiest 20% has an unjust burden placed on them
3) Actual (Senator's position): the tax system does not impose a greater hardship on the wealthiest 20%

Whenever you're asked to resolve a discrepancy with mathematical language, think about mathematical METRICS. If everyone made exactly the same amount of money, 20% of people should pay 20% of taxes. If the wealthiest people make significantly more money than other people, they could pay a lot more money in taxes (accounting for a larger percentage of the total pool of tax revenue), without necessarily paying a larger proportion of their income in taxes than anyone else does.

We're looking at two different proportions here: the proportion of the total pool of tax revenue v. proportion of each person's income. To resolve the apparent paradox, we need to say that the taxes from these 20% make up a 70% portion of all tax revenue, but that these people do not pay taxes at a higher rate (a greater proportion of their income) than anyone else.

A. Supplemented income does not answer the question of whether they are taxed at a higher rate.

B. Ability to pay taxes does not address whether they are taxed unfairly.

C. The tiered rate could give a much higher rate to the wealthy, supporting the Congressperson's claim.

D. The argument only talks about income tax revenue. Irrelevant.

E. If the wealthiest earn 75% of income but only pay 70% of income taxes, they are actually taxed at a lower rate than the total population, and thus do NOT have an unjust burden placed on them. Correct.

The answer is E.