Concept:A tax system is identified by comparing tax rates at different income levels.Explanation:Mr. X earns $5,000 and pays $500 as tax.His tax rate is 5,000500×100=10%.Mrs. Y earns $7,000 and pays $1,400 as tax.Her tax rate is 7,0001,400×100=20%.As income rises, the tax rate also rises from 10% to 20%.This means higher income earners pay a higher percentage of their income as tax.Answer:D. progressive tax