When you approach a railroad crossing, what should you do?

Answer: D — Stop and check for trains

When approaching a railroad crossing, it is important to pay close attention and take the necessary precautions. This includes stopping and checking for oncoming trains before proceeding. Options A and B do not directly address the potential danger of a train, and option C is not a safe or legal action to take when approaching a railroad crossing. Therefore, option D is the best choice when approaching a railroad crossing.