Answer:
The correct answer is A. When the arrector pili muscles contract, goose bumps form.
Explanation:
The arrector pili muscle of the hair is composed of smooth muscle fibers and receives innervation from the sympathetic nervous system. It is inserted into the hair follicle, in its middle section, with an oblique direction, and when it contracts it tenses the hair and puts it straight, which is known as goose bumps.
