By law, when must the warning lights be used?

The correct answer highlights the legal requirement to use warning lights specifically when approaching a stop to load or unload students. This is a critical safety measure designed to alert other drivers and ensure that they slow down and exercise caution in the vicinity of a school bus. By activating warning lights, drivers create a clear visual signal that children may be entering or exiting the bus, thereby helping to prevent accidents and enhance the safety of students.

Other scenarios, such as driving over a certain speed or maneuvering through busy intersections, do not inherently require the use of warning lights. The usage of warning lights is particularly focused on protecting children during pickup and drop-off times, which is why it is mandated by law in this context. Additionally, while making sharp turns may require attention to safety and sometimes turning signals, it does not involve the same level of risk concerning student safety as when they are loading or unloading.