Final answer:
The hair bulb is the part of the hair that resembles the shape of a golf club. It is located at the base of the hair root and is where new hair is produced.
Step-by-step explanation:
The part of the hair that resembles the shape of a golf club is the hair bulb. Unlike the other listed structures like the papilla, which is a mass of connective tissue located at the base of the hair follicle, or the hair shaft, which is the part of the hair that is visible from the outside, or the arrector pili muscle, a smooth muscle that creates goose bumps when it contracts, the hair bulb is the structure at the base of the hair root that surrounds the dermal papilla and has a shape most closely resembling that of a golf club head. It serves as the site where new hair is generated from the hair matrix, a layer of basal cells.