During which phase does hair growth predominantly occur?

Hair growth predominantly occurs during the anagen phase, which is the active growth phase of the hair cycle. During this time, hair follicles are highly active and producing new cells, which are released as hair fibers. This phase can last for several years, and the duration contributes to the length and thickness of the hair.

In contrast, other phases do not support significant hair growth. The telogen phase is the resting phase, where hair is not actively growing and may eventually shed. The catagen phase is a transitional phase during which growth slows and hair follicles begin to shrink. The exogen phase refers to the period of shedding, where old hairs fall out to make way for new growth. Therefore, the anagen phase is critical for substantial hair production, making it the correct answer.