An income tax is progressive if the

absolute amount paid as taxes varies directly with income

percentage of income paid as taxes is the same regardless of the size of income

percentage of income paid as taxes increases as income increases

tax rate varies inversely with income

Option C - An income tax is progressive if the percentage of income paid as taxes increases as income increases.

Explanation:

Majorly, there are three types of Tax systems; these are: Progressive, regressive and proportional.

A tax in which the tax rate increases as the taxable amount increases is known as a progressive tax.

The term "progressive" refers to the way the tax rate progresses from low to high, such that a taxpayer's average tax rate is less than the person's marginal tax rate.

Also, a progressive tax is applicable to individual taxes or to a tax system as a whole; a year, multi-year, or lifetime. It is imposed with the aim of reducing the tax incidence of people with a lower ability to pay, as such taxes shift the incidence increasingly to those with a higher ability-to-pay.

Thus, an income tax is progressive if the percentage of income paid as taxes increases as income increases.