According to FMCSA guidelines, which action is permissible while driving a commercial motor vehicle (CMV)?

Answer: C — Answering a hands-free cell phone by touching a single button

The action of answering a hands-free cell phone by touching a single button is permissible according to FMCSA guidelines because it allows the driver to maintain a level of focus on driving while managing a communication device. Hands-free use minimizes distractions, enabling the driver to keep both hands on the steering wheel and maintain their attention on the road. The guidelines are specifically designed to enhance safety on the roads by limiting actions that could divert a driver's attention. While other options involve using a phone in a way that could be distracting or require more significant manipulation, touching a single button to answer a call does not compromise the driver's ability to control the vehicle effectively. This distinction is crucial for ensuring that the driver remains safe while engaging with necessary communication.