Which of the following behaviors is a sign of redirected aggression?

Redirected aggression occurs when a dog becomes agitated or aggressive towards a target that is not the original source of its frustration or fear. This usually happens when a dog is unable to reach the initial target, often due to restraint or distance, leading to an outburst directed at a more convenient or nearby target.

In this case, snapping at a bystander trying to help indicates that the dog is overwhelmed or frustrated by the situation and cannot express its aggression toward the original cause, which might be another dog or a stressful event. This reaction can be unpredictable and is a clear demonstration of redirected aggression because the bystander, who poses no threat, is unjustly targeted due to the dog's inability to direct its aggression elsewhere.

The other behaviors listed do not characterize redirected aggression. Barking at a different dog can be a form of communication or assertiveness but does not signify misdirected hostility. Attacking an intruder is a direct response to a perceived threat and not a misdirected action. Cowering in fear signifies submission or anxiety rather than aggression. Thus, the choice of snapping at a bystander captures the essence of redirected aggression effectively.