To examine a patient`s abdomen (alimentary canal) using X-ray, a metal salt is administered in the patient`s meal. The purpose of administering this metal salt is to make the alimentary canal more visible in the X-ray images.

Option 1: Barium sulphate is the correct answer. Barium sulphate is commonly used as a contrast agent in X-ray examinations of the gastrointestinal tract. It is safe to consume and does not get absorbed by the body, allowing it to pass through the gastrointestinal tract and provide a clear outline of the organs and structures in the area.

Option 2: Barium chloride is not commonly used for this purpose. It is sometimes used as a contrast agent in certain medical imaging procedures but not specifically for examining the abdomen.

Option 3: Strontium sulphate is not commonly used as a contrast agent in X-ray examinations of the abdomen. It is occasionally used for other imaging studies, but barium sulphate is more commonly preferred.

Option 4: Magnesium chloride is not used as a contrast agent for X-ray examinations of the abdomen. It has different applications and is not suitable for this purpose.

In conclusion, the correct metal salt that is administered in the patient`s meal to examine the abdomen using X-ray is barium