Tower drives a truck for Musgrove Produce, Inc. The truck is owned by Musgrove. Tower is paid on the basis of a formula that takes into consideration the length of the trip, cargo, and fuel consumed. Tower is responsible for repairing or replacing all flat tires. Musgrove is responsible for all other truck maintenance. Tower drives only for Musgrove. If Tower is a common-law employee and not an independent contractor, which of the following statements is true?

A. All Social Security retirement benefits are fully includible in the determination of Tower's federal taxable income if certain gross income limitations are exceeded.
B. Musgrove remains primarily liable for Tower's share of FICA taxes if it fails to withhold and pay the taxes on Tower's wages.
C. Musgrove would not have to withhold FICA taxes if Tower elected to make FICA contributions as a self-employed person.
D. Bonuses or vacation pay that are paid to Tower by Musgrove are not subject to FICA taxes because they are not regarded as regular compensation.

Answer: B. Musgrove remains primarily liable for Tower's share of FICA taxes if it fails to withhold and pay the taxes on Tower's wages.