Which part of the gilt can tear off and cause unsoundness if it touches the ground while traveling?

The dewclaw is the correct answer because it is a small, vestigial digit located higher up on the leg, which does not touch the ground under normal circumstances. If the dewclaw makes contact with the ground while the animal is moving, it can get caught or snagged, leading to tearing or injury. Such injuries can result in unsoundness, which is a term used to describe conditions that affect the animal's ability to move properly or maintain good health.

In contrast, the tail, ears, and teats do not typically correspond to the type of injury described. The tail can be more flexible and often does not pose a risk of tearing in the same way, while the ears are not involved in locomotion at all. Teats are primarily involved in nursing and would not be at risk of tearing from ground contact during travel. Therefore, the dewclaw stands out as the specific body part that can be affected in this way, making it the correct choice.