Which of the following actions can be classified as racing behavior?

Racing behavior typically involves two or more vehicles actively competing against each other at high speeds, often on public roads. This type of conduct is dangerous and illegal, as it can lead to serious accidents due to the excessive speeds and unpredictable maneuvers. In the context of the options provided, the action of two or more people racing on a highway embodies the essence of racing behavior, characterized by a competitive intent and the expectation of speed exceeding safe limits.

In contrast, speeding up to allow another car to merge is a courteous driving action aimed at maintaining smooth traffic flow, not a competitive or racing situation. Driving under the speed limit and stopping at all traffic signals indicate compliance with traffic laws and safe driving practices, which further emphasize responsible behavior on the road rather than racing. Therefore, the option that describes racing behavior most accurately is the one involving multiple vehicles racing on a highway.