How can you determine your following distance?

Answer: B — By counting seconds after a landmark is passed

Counting seconds after a landmark is passed serves as an effective method for determining your following distance. This technique is based on a well-established rule of thumb known as the "three-second rule." When driving, you can mark a fixed point, such as a sign or a tree, and then start counting as the rear of the vehicle in front of you passes that point. If you reach the landmark before you've counted to three seconds, it indicates that you are following the vehicle too closely. This method accounts for varying speeds and conditions; it gives a universal measurement that applies regardless of vehicle size or speed. Proper following distance is crucial for ensuring there is enough time to react to sudden stops or emergencies, helping to maintain safety on the road. The other options do not provide a reliable method for assessing following distance. Checking the speedometer may help you gauge your speed but does not indicate how close you are to the vehicle ahead. Measuring distance with a ruler is impractical for on-the-road driving. Observing the vehicle's speed alone can provide context, but without a clear method of measurement regarding distance, it does not effectively ensure safety.