Which rule must drivers follow in the case of limited passing of oncoming traffic on sections of road marked with the signs "Steep Ascent" and "Steep Descent"?

• 1The driver in whose lane there is an obstruction must give way.
• 2The driver of the vehicle whose dimensions hinder the passing of oncoming traffic must give way.
• 3Answers 1 and 2.
• 4The driver of the vehicle travelling downhill must give way.