Concept:Regressive tax takes a larger percentage of income from low-income earners than from high-income earners.Explanation:Tax rate is calculated as tax paid divided by income.For Mr. A, tax rate =2000200=0.10=10%.For Mr. B, tax rate =8000400=0.05=5%.Mr. A earns less but pays 10% of his income as tax.Mr. B earns more but pays only 5% of his income as tax.Thus, the percentage of income taken as tax decreases as income increases.This pattern shows that lower-income earners bear a heavier tax burden relative to their income.Therefore, such a tax system is classified as regressive.Answer:D. Regressive