Step 1: What does an adsorbent do in diarrhoea?
An adsorbent coats the gut wall and binds toxins, bacteria, and irritants on its surface, reducing their contact with the intestinal mucosa and helping to firm up stools.
Step 2: Review the options.
Ferrous Sulphate is an iron supplement. Calcium Carbonate is an antacid. Magnesium Hydroxide is a laxative. Light Kaolin is a naturally occurring hydrated aluminium silicate clay.
Step 3: Kaolin as an adsorbent.
Light Kaolin has a very large surface area. It physically adsorbs bacteria, toxins, and irritants in the gut lumen. It is one of the oldest anti-diarrhoeal adsorbents and is official in the British Pharmacopoeia.
Step 4: Why the distractors are wrong.
Ferrous sulphate and calcium carbonate do not have adsorptive action in the gut. Magnesium hydroxide actually increases gut motility and causes diarrhoea rather than treating it.
Step 5: Conclusion.
Among the inorganic compounds listed, Light Kaolin is specifically used as an adsorbent anti-diarrhoeal agent.
Answer: Option (3) — Light Kaolin