Correct Answer: Income tax

Solution : The correct answer is (a). Income tax.

Income tax is the primary source of revenue for the federal government in the United States. The federal government collects income tax from individuals, households, and businesses based on their income and profits. This tax is levied at both the federal level and, in some cases, at the state level.

Income tax is collected through various means, including withholding from wages and salaries, estimated tax payments, and annual income tax returns. The tax rates and brackets vary depending on an individual's or business's taxable income.