Final answer:
The correct answer is (b) catagen, which is the transitional phase in the hair growth cycle that follows the growth (anagen) phase and precedes the resting (telogen) phase, where the hair bulb disappears and prepares the follicle to eventually shed the hair.
Step-by-step explanation:
During the catagen phase, the hair bulb disappears, which signifies the end of the growing period and the beginning of the transitional phase. The catagen phase is a short transitional stage that follows the anagen (growth) phase of the hair growth cycle. This phase marks the cessation of active hair growth and the hair follicle's preparation to enter the telogen phase, where the hair is in a resting state before it is eventually shed at the end of this cycle. Within the hair follicle structure, the cortex is considered the second or middle layer of keratinocytes originating from the hair matrix, as seen in a cross-section of the hair bulb.
The question pertains to the hair growth cycle, whose phases contribute to the overall process of hair regeneration and shedding. Abnormalities in this cycle can lead to hair loss due to various factors such as hormonal or dietary changes, aging, or the influence of hormones.