**Core Concept**
The growth phase of hair, also known as the anagen phase, is a critical period of hair follicle activity where the hair grows rapidly. This phase is characterized by intense mitotic activity, leading to the elongation of the hair shaft.

**Why the Correct Answer is Right**
The anagen phase is the longest phase of the hair growth cycle, lasting anywhere from 2-6 years, with an average duration of 3 years. During this phase, the hair grows at a rate of about 1 centimeter per month. The increased mitotic activity is due to the presence of a large number of stem cells in the hair follicle, which are stimulated by growth factors such as keratinocyte growth factor (KGF) and vascular endothelial growth factor (VEGF). The hair shaft is also compacted and hardened by the deposition of melanin, giving it its characteristic color and strength.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the anagen phase is not the shortest phase of hair growth. The anagen phase is the longest phase, followed by the catagen phase and then the telogen phase.
**Option B:** This option is incorrect because the hair growth rate during the anagen phase is not 1 centimeter per week, but rather 1 centimeter per month.
**Option C:** This option is incorrect because the anagen phase is not the phase where hair follicles are in a resting state. The anagen phase is characterized by intense mitotic activity.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the anagen phase can be affected by various factors, such as genetics, hormones, and certain medical conditions, which can lead to changes in hair growth patterns and density.

**Correct Answer: C.**