Pepsin is an enzyme that is primarily found in the stomach and plays a crucial role in the digestion of proteins. It is secreted by the gastric chief cells in an inactive form called pepsinogen, which is then activated by the acidic environment of the stomach. Once activated, pepsin breaks down proteins into smaller peptide fragments and eventually into individual amino acids, which can be absorbed by the body.

Pepsin acts through a process called hydrolysis, which involves the addition of a water molecule to break the peptide bonds that hold the amino acids together in a protein. This process is essential for the body to obtain the necessary amino acids for various physiological functions, such as the synthesis of new proteins, enzyme activity, and hormone production.

To better understand why the correct answer is option 'C' (proteins to amino acids), let's break down the other options and eliminate them:

a) Polysaccharides to monosaccharides: This process is actually carried out by enzymes called amylases, not pepsin. Amylases are found in saliva and pancreatic secretions and are responsible for breaking down complex carbohydrates (polysaccharides) into simpler sugars (monosaccharides) such as glucose.

b) Glucose to ethyl alcohol: This process is not mediated by pepsin but rather by a different enzyme called yeast. Yeast is able to convert glucose into ethyl alcohol through a process called fermentation.

d) Fats to fatty acids: The digestion of fats involves the action of enzymes called lipases, not pepsin. Lipases break down fats (triglycerides) into fatty acids and glycerol, which can then be absorbed by the body.

In summary, pepsin is specifically responsible for hydrolyzing proteins into amino acids. This process is crucial for the body to obtain the necessary building blocks for protein synthesis and various other physiological functions.