What is a consequence of passing another vehicle when the speed difference is slight?

Answer: C — Bunching of vehicles creating a hazard

Passing another vehicle when the speed difference is slight can create a dangerous situation known as "bunching." This happens when the passing vehicle is moving at a similar speed as the vehicle being passed, causing both vehicles to travel next to each other for an extended period of time. This can create a hazard as it reduces the visibility of both vehicles and can make it difficult for other drivers to pass. Additionally, it can cause frustration and aggressive driving behaviors, increasing the risk of accidents. The other options, such as increased fuel efficiency and improved vehicle control, are not directly related to passing another vehicle when the speed difference is slight and do not address the potential danger of bunching. Therefore, they are incorrect options.