Answer: c. FICA.
Step-by-step explanation: Law requires particular payroll deductions. We do not pay taxes on Flexible spending accounts, because these are the specials accounts from where we pay off for certain health care issues, so, option (a) is incorrect. A private retirement account offers us to save tax-free amount for our retirement and so option (b) will also not work. FICA (Federal Insurance Contributions Act.) includes social security taxes, medicare taxes, etc. and so this option is correct.
Thus, the answer is (c). FICA.