Which of the following statements about bandage layers is true?

The primary layer of a bandage is crucial as it directly contacts the wound. This layer should always be sterile to prevent infection and promote healing. If the primary layer is not sterile, it can introduce bacteria into the wound, exacerbating the injury and delaying recovery. Using sterile materials helps maintain a clean environment for healing.

The other statements don't hold true in the context of bandaging. For instance, the tertiary layer is not required to be made of gauze; it can be composed of various materials, including elastic or cohesive bandages, designed to protect the underlying layers while being flexible. The secondary layer plays a vital role in providing support and cushioning, though in certain situations, such as simple or minor injuries, it might be deemed unnecessary by a veterinarian. Lastly, each layer in a bandaging system serves distinct functions: protecting the wound, providing support, and securing the bandage, which is why they are not interchangeable and do not serve the same purpose.