It starts raining. Why must you immediately increase the safe distance?

Your answer is correct. When it starts raining, a greasy film can form on the road surface, especially if it hasn't rained for a while, which makes the road more slippery and increases braking distance. Additionally, rain reduces visibility because the windscreen wipers take a moment to clear the water, so your view of the traffic ahead is temporarily impaired. Both factors make it important to increase the safe distance immediately to allow more reaction and braking time. The third option is incorrect because brakes do not react more quickly in rain; in fact, braking can be less effective due to slippery conditions.