Under what circumstances may you drive to the left of a yellow line?

Answer: B — When the right side of the road is closed or obstructed

Driving to the left of a yellow line is permissible primarily when the right side of the road is closed or obstructed. This situation arises in scenarios such as construction zones, where barriers or debris prevent safe travel on the right side, necessitating movement into oncoming traffic's lane to maintain forward travel. Safety regulations allow crossing a solid yellow line when it is a practical necessity due to such obstructions, as long as it can be done safely and without causing danger to other road users. Other options, like passing another vehicle, may require specific conditions and could also involve additional legal restrictions, such as the markings of the road and visibility. Thus, while it might be common practice to pass on the left, it's not an absolute rule, and similarly, backing out does not generally warrant crossing a yellow line safely. Nighttime driving does not inherently change the rules around yellow lines; rather, the focus is always on road conditions and safety.