When applying a cast, plaster is applied over a stockinette and padding to protect the skin and provide comfort. The stockinette is a soft, stretchable fabric sleeve that prevents direct contact between the plaster and the skin. The padding, often made of cotton or synthetic materials, cushions the area and absorbs any moisture. The other options are incorrect and can lead to complications such as skin irritation or pressure sores.
Reference:
"Cast Care Instructions." American Academy of Orthopaedic Surgeons, https://orthoinfo.aaos.org/en/recovery/caring-for-casts-and-splints