Which of the following is an example of a skin appendage?

Hair follicles are indeed a prime example of skin appendages. Skin appendages are structures that develop from the epidermis and are embedded within the dermis. Hair follicles serve various functions, such as producing hair, which provides protection, regulates body temperature, and contributes to the sense of touch.

In contrast, nerve endings, while crucial for sensation, do not form from the epidermal layer and are classified as sensory receptors rather than appendages. Blood vessels, also not considered skin appendages, are part of the circulatory system and facilitate blood flow, delivering nutrients and oxygen to the skin rather than originating from it. Dermal papillae enhance the connection between the epidermis and dermis and play a role in fingerprint formation, yet they do not extend outwards like appendages do. Thus, hair follicles are the correct representation of the category in question.