Stomach's role in digestion and sterilization

Steps:

• Identify the question: organ producing acid to kill bacteria in food.
• Recall digestive system functions: stomach secretes gastric juice containing hydrochloric acid (HCl).
• Understand HCl's role: lowers pH to 1-2, creating acidic environment that destroys bacteria.
• Eliminate non-acid-producing organs for this purpose.

Why D is correct:

• The stomach produces hydrochloric acid (HCl), which denatures proteins and kills ingested bacteria by creating a highly acidic environment (pH 1-2), as per gastric physiology.

Why the others are wrong:

• A. Liver: Produces bile for fat emulsification, not antibacterial acid.
• B. Pancreas: Secretes alkaline enzymes and bicarbonate to neutralize stomach acid, not produce killing acid.
• C. Salivary gland: Produces saliva with amylase for starch breakdown and mild antibacterial lysozyme, but no strong acid.

Final answer: D