Final answer:
When approaching a snowplow truck, you must maintain a safe distance to avoid damage from debris and to provide adequate reaction time should the snowplow stop unexpectedly.
Step-by-step explanation:
When you approach a snowplow truck in winter driving, you must maintain a safe distance to avoid any kind of damage. Hence, the correct answer is 1) a safe distance. Maintaining a safe distance is crucial because snowplow trucks may be spreading salt or sand, and they can also create snow clouds that reduce visibility. If you follow too closely, your vehicle can be hit with debris, or you might not be able to react in time if the snowplow stops or slows down suddenly.