When passing a snowplow, it's important to know the wing on its right can extend how far across the road?

Answer: C — 3 metres

When passing a snowplow, it's important to know the wing on its right can extend up to 3 meters across the road. This is because a snowplow's wing extends farther out than a typical vehicle, and not knowing this could result in a dangerous situation if the snowplow's wing comes into contact with your vehicle. Option A and B are incorrect because they do not extend far enough, and option D is incorrect because it overestimates the width of the wing. It's important to always be cautious and give snowplows enough space when passing to avoid any accidents on the road.