Which one is the most abundant protein in the animal world?

Correct option: C

Explanation:

• The most abundant protein in the animal world is Collagen. It is found in the extracellular matrix of connective tissues like cartilage, bones, tendons, ligaments, and skin.
• Trypsin is an enzyme which hydrolyses proteins into smaller peptides in the small intestine. It is produced as the inactive zymogen trypsinogen in the pancreas.
• Haemoglobin is a iron-containing oxygen-transport protein found in red blood cells.
• Insulin is a peptide hormone produced by beta cells of the pancreatic islets in response to high level of blood glucose.
  Thus, Option C is correct.