By what hour must all tour groups be disbanded nightly according to the regulations?

The correct answer reflects the regulations set forth for tour groups operating in New Orleans, which contribute to maintaining the balance between tourism and the local community's peace during nighttime hours. By having all tour groups disband by 10:00 pm, the city aims to minimize disturbances that may arise from larger gatherings of tourists in popular areas.

This time restriction is essential for preserving the residential nature of certain neighborhoods and ensuring that local residents can enjoy their evening without the noise and bustle associated with tour groups. Additionally, this cutoff time helps guides and participants wrap up their activities in a safe and organized manner, thus contributing to the overall experience of both visitors and locals.

The other options suggest either an earlier or later disbanding time, which would not align with the city's efforts to promote a harmonious atmosphere during the late evening. Hence, the regulation specifically designating 10:00 pm as the cutoff underscores the importance of responsible tourism.