Answer:
The correct answer is option A. "skin".
Step-by-step explanation:
Hair and nails are derived from cells of the skin. The cells of the skin have keratin, a protein that creates a protective barrier against the environmental factors that could affect them. The hair and nails are modifications of skin cells, that have keratin but with additional features. The hair is made of 95% keratin and is formed of three components: medulla, cuticle and cortex. The nail cells are made from keratin as well, forming a horn-like structure that is replaced by skin cells constantly.