When is the use of the horn prohibited?

The correct choice is the prohibition of horn use between 11:30 pm and 7:00 am in a built-up area. This regulation is in place primarily to minimize noise pollution during late-night and early-morning hours when residents are likely to be sleeping. The use of the horn during these times can be disruptive and disturbing, particularly in areas where homes are closely situated together.

Maintaining peace and quiet during these hours is important for community living, and regulations like this help ensure that drivers are considerate of the residents in urban environments. In contrast, other options suggest circumstances for horn use or prohibitions that may not align with the specific regulations aimed at preserving nighttime tranquility in built-up areas.