A vehicle driver must slow down when he:

1. Overtakes on a two-way road.
2. Arrives to the beginning of a steep uphill climb.
3. Overtakes on a one-way road.
4. Correct answer: Drives down a steep or long descent.

WhyOn a steep or long descent the law requires you to slow down. It is not required before a climb, and you do not slow down while overtaking.