What is the purpose of using air conditioning while driving?

Using air conditioning while driving primarily serves the purpose of helping to defog the interior windows. When the air conditioning system is engaged, it not only cools the air but also dehumidifies it. This reduction in humidity helps prevent condensation on the windows, which is especially important in conditions where warmth from passengers or external moisture could cause fogging.

In contrast, while the other options may appear relevant in a broad context, they do not accurately reflect the primary function of air conditioning while driving. Increasing fuel efficiency is typically associated with having the windows closed, and while air conditioning can sometimes improve comfort and performance, it is not directly related to enhancing engine performance or significantly reducing engine noise. The primary role of air conditioning in warm or humid conditions is indeed to maintain visibility by managing fog on the windows, making option B the most accurate choice.