The federal income taxes that are withheld from your paycheck are used to pay for what?

The correct answer is a. Mandatory spending.

Federal income taxes that are withheld from your paycheck primarily fund mandatory spending programs, which include essential services such as Medicare and Social Security. These programs are required by law to be funded and are critical for supporting individuals and families in need. Discretionary spending, on the other hand, is determined through the annual appropriations process and includes areas like defense and education, while unemployment insurance is a specific program supported by payroll taxes.