Which program must drivers operating in the U.S. participate in?

Answer: B — Drug and alcohol testing program

All drivers operating in the U.S. are required by law to participate in a drug and alcohol testing program. This ensures that drivers do not operate vehicles while under the influence of substances that can impair their abilities to drive safely. The other programs listed may be related to driving safety, but they are not mandatory for all drivers. Speed management programs may be recommended, but not required. Hazardous materials awareness programs may be necessary for truck drivers, but not all other drivers. Eco-driving programs may promote environmentally-friendly driving habits, but they are not required by law. Therefore, B is the only correct answer.