When a truck breaks down on a highway during the daytime, what should the driver set out?

Answer: B — Red triangles

When a truck breaks down on a highway during the daytime, setting out red triangles is important for ensuring safety. Red triangles are a standardized warning device that effectively alert other drivers to the presence of a vehicle that has stopped or is disabled on the roadway. Using red triangles provides a clear visual indication that there is an obstacle ahead, prompting other drivers to slow down and navigate carefully around the situation. The bright color and reflective properties of the triangles enhance visibility even in daylight, making them an effective choice for daytime breakdowns. While other options like flares, cones, or warning signs can be useful in certain situations, red triangles are specifically designed and mandated for use in these types of roadside emergencies. They help maintain the safety of both the driver and passing vehicles by providing a standardized warning that is recognized by all drivers.