According to FMCSRs, what is required to operate a commercial motor vehicle (CMV)?

Answer: B — Holding only one current commercial driver's license (CDL)

Holding only one current commercial driver's license (CDL) is an important requirement for operating a commercial motor vehicle (CMV) as stipulated by the Federal Motor Carrier Safety Regulations (FMCSRs). The CDL is specifically designed to ensure that drivers have the necessary knowledge and skills to safely operate large and complex vehicles used in commercial activities. The requirement to have only one CDL is crucial because it helps maintain a clear and verifiable record of a driver's qualifications and history. Multiple licenses can lead to confusion regarding a driver's safety record and may complicate issues related to accountability and regulation enforcement. Moreover, a single CDL ensures that the driver adheres to the regulations and standards set for CMV operators, maintaining safety on the road. The other choices, while they may relate to driving qualifications, do not meet the specific requirements outlined for operating a CMV under FMCSRs. For example, possessing a motorcycle license does not qualify someone to drive a CMV, and while the minimum age of 21 years is relevant for interstate operations, it's not the only requirement. Additionally, completion of a defensive driving course, while beneficial for overall driving safety, is not a formal requirement under the FMCSRs specifically for obtaining a CDL.