What should you do when approaching a railroad crossing with lowered gates or an oncoming train?

Answer: A — Stop your vehicle before reaching the gates

When approaching a railroad crossing with lowered gates or an oncoming train, it is important to stop your vehicle before reaching the gates. This is the safest option because it allows you to assess the situation and wait for the train to pass before proceeding. Option B, speeding up and going through quickly, is incorrect because it can be dangerous and illegal. Option C, sounding your horn, may not be effective in warning the train or other vehicles on the road. Option D, reversing, is also not a recommended option as it can be difficult to judge the distance between your vehicle and the oncoming train. Therefore, stopping your vehicle before the gates is the most appropriate and safe action to take when approaching a railroad crossing with lowered gates or an oncoming train.