Question

which element is most important for adding strength to hair, feathers, and outer skin?
○ oxygen
○ hydrogen
○ sulfur
○ phosphorus

Explanation:

Hair, feathers, and outer skin contain keratin, a protein. Sulfur forms disulfide bonds in keratin, which are crucial for the structural strength and stability of these structures. Oxygen, hydrogen, and phosphorus do not play this specific role in adding strength to these tissues.

Answer:

C. sulfur