Which of the following is a mandatory withholding from officer paychecks?

Social security taxes are a mandatory withholding from officer paychecks because they are a part of the federal payroll tax system established under the Federal Insurance Contributions Act (FICA). This tax is imposed on both employees and employers to fund Social Security and Medicare benefits.

The requirement to withhold social security taxes applies to all employees, including officers, and is calculated based on a percentage of their earnings. This ensures that individuals contribute to their future retirement benefits and health coverage under Medicare.

On the other hand, medical insurance premiums, gratuities, and equipment costs may be related to an employee's compensation package but are not mandated by federal or state law as automatic withholdings. Medical insurance premiums are typically voluntary deductions that employees can choose to participate in, gratuities are earned based on service and are not wages, and equipment costs are usually considered personal expenses unless otherwise specified by an employer.