Which of the following would result in a penalty besides a score of 0?

The scenario where breaking gait at the lope for more than two strides is likely to result in a penalty beyond a score of 0 is correct because it indicates a significant disruption in the performance of the horse. In competitive equine events, maintaining the correct gait is crucial as it reflects the horse's training and the rider's control. Breaking the designated gait, especially for an extended period, demonstrates a lack of precision and can lead to penalties that affect the overall score. This kind of fault shows a fundamental error in the execution of required movements and is treated seriously in judging.

While other options present instances of faults, they may not always lead to a comparable level of penalty. For example, a horse rearing at the halt can be penalized as well, but it might be contextual as to whether it results in a score of 0 or merely a deduction. Similarly, a horse jumping the fence might indicate a misunderstanding of the course rather than a failure to follow the required movements or gaits. Dropping a rein is often considered a minor fault, often resulting in minor deductions rather than severe penalties. Thus, the nuance in performance evaluation means that breaking gait at the lope for an extended duration is viewed as a more serious issue within the context