Which substances are CDL drivers prohibited from using within four hours before operating a vehicle?

Answer: B — Alcohol and drugs

CDL drivers are prohibited from using alcohol and drugs within four hours before operating a vehicle to ensure safety on the roads. This regulation is in place because both substances can impair a driver's ability to operate a vehicle safely, leading to a higher risk of accidents. The stipulation for the four-hour timeframe emphasizes the importance of ensuring drivers are fit to operate commercial vehicles, which can be significantly larger and more difficult to control than standard vehicles. Alcohol consumption, in particular, affects cognitive functions, coordination, and reaction times, all essential for safe driving. Illegal drugs can have similar effects, and even some legal substances can lead to impairment. By enforcing this rule, regulatory bodies aim to minimize the risk of impaired driving among commercial drivers, thus enhancing road safety for everyone.