A type of tax that increases proportionally as income increases:

Regressive tax
Progressive tax
Flat tax
Proportional tax

The correct answer is: B) Progressive tax.

A progressive tax is a tax that takes a larger percentage of income from high-income earners than from low-income earners. This is in contrast to a regressive tax, which takes a larger percentage of income from low-income earners than from high-income earners.

A proportional tax is a tax that takes the same percentage of income from all taxpayers, regardless of their income level.

A flat tax is a type of proportional tax in which everyone pays the same amount of tax, regardless of their income level.

Here is a table that summarizes the key differences between progressive, regressive, and proportional taxes:

| Type of tax | How much tax is paid | Example |
|—|—|—|
| Progressive tax | Higher-income earners pay a larger percentage of their income in taxes | Income tax in the United States |
| Regressive tax | Lower-income earners pay a larger percentage of their income in taxes | Sales tax |
| Proportional tax | Everyone pays the same percentage of their income in taxes | Flat tax |

It is important to note that the classification of a tax as progressive, regressive, or proportional can vary depending on the specific tax system in question. For example, the United States income tax system is generally considered to be progressive, but there are some aspects of the system that could be considered regressive.