Ans is 'a' i.e. the phase of activity and growth Hair cycle and growthThe hair during its life, passes through three different phases of growth and shedding. This cycle is independent of the cycle of the neighbouring follicles i.e. the neighbouring follicles are not synchronized in growth. These stages of hair cycle areAnagen - The phase of activity and growthCatagen - The phase of transitionTelogen - The phase of resting (degenerative state)The proportion of hair in each phase can be estimated by looking at the plucked hair - this is called Trichogram. Anagen phase - growth phaseApproximately 85% of all hairs in the growing phase at any one time.The angen phase or growth phase can vary from two to six year.Hair grows approximately 10 cm per year and any individual hair is unlikely to grow more than one metre long.Catagen phase - transitional phaseAt the end of the Anagen phase the hairs enters into a catagen phase which lasts about one or two weeks.During the catagen phase the hair follicle shrinks to about 1/6, dermal papilla breaks away to rest below Telogen phase - resting phaseThe resting phase follows the catagen phase and normally lasts about 5-6 weeks.During this time the hair does not grow but stays attached to the follicle while the dermal papilla stays in a resting phase below.Approximately 10-15% of all hairs are in this phase at one time.At the end of the Telogen phase the hair reenters the anagen phase. The dermal papillae and the base of follicle join together, and a new hair begins to form. If the old hair has not already been shed the new hair pushes the old one out and the growth cycle starts all over again.