Which of the following is a situation where stopping or parking is not allowed?

Stopping or parking within 3 meters of a vehicle entrance to a main road is not allowed because this distance is regulated to ensure that there is adequate visibility and space for vehicles entering or exiting the roadway. This regulation is intended to minimize the risk of accidents, as parking too close can obstruct the line of sight for drivers, making it difficult for them to see oncoming traffic. The rule also aids in maintaining a smooth traffic flow by ensuring that vehicles can navigate the entrance to the main road comfortably without obstruction.

In contrast, parking in a designated parking lot, on public roads during daytime (as long as other parking regulations are adhered to), and waiting at a red light are generally permitted under the right circumstances, making option A the clear choice for a situation where stopping or parking is prohibited.