Which muscle is responsible for the formation of goosebumps?

The muscle responsible for the formation of goosebumps is the arrector pili. When the body experiences cold temperatures or emotional responses such as fear, the arrector pili muscles contract. This contraction causes the hair follicles to be pulled upright, resulting in the appearance of goosebumps on the skin. This reflex action is part of the body's thermoregulation process and is often considered a vestigial reflex inherited from our animal ancestors, where it helped to trap air for insulation or make them appear larger in the face of threats.

The other options are related to skin and hair but serve different functions. Sebaceous glands produce oil that moisturizes the skin and hair, collagen is a protein that provides structure and elasticity to the skin, and pheomelanin is a type of melanin responsible for lighter hair colors. While these elements are important for skin and hair health, they are not directly involved in the formation of goosebumps. Therefore, the arrector pili muscle is the correct answer in the context of this question.