### Core Concept
Inhaled sodium cromoglycate is a mast cell stabilizer that blocks the release of histamine and other mediators involved in allergic inflammation. It acts by inhibiting the degranulation of mast cells, thereby preventing the antigen-antibody complex from triggering the allergic response.

### Why the Correct Answer is Right
Sodium cromoglycate works by stabilizing the mast cell membrane, preventing the release of histamine and other chemical mediators. This action is crucial in preventing exercise-induced bronchial spasm, which is a common symptom of exercise-induced asthma. The drug is particularly effective in this context because it can be administered directly to the lungs, where it can exert its effects locally. This targeted approach helps to minimize systemic side effects and maximize efficacy.

### Why Each Wrong Option is Incorrect
**Option A:** This is incorrect because sodium cromoglycate does not prevent the antigen-antibody combination itself, but rather blocks the downstream effects of this interaction, specifically the release of histamine and other mediators.

**Option B:** This is incorrect because sodium cromoglycate is not associated with cardiac arrhythmias as a side effect. Its mechanism of action is focused on preventing allergic inflammation, rather than affecting cardiac function.

**Option D:** This is incorrect because sodium cromoglycate is not effective in alleviating an acute episode of allergic asthma. Its role is preventive, rather than therapeutic, and it is best used to prevent symptoms from occurring in the first place.

### Clinical Pearl / High-Yield Fact
It's worth noting that sodium cromoglycate is a non-steroidal, non-bronchodilator medication, making it an attractive option for patients who require long-term management of asthma or allergic rhinitis. Its mechanism of action as a mast cell stabilizer is distinct from other classes of asthma medications, such as corticosteroids and beta-agonists.

### Correct Answer Line
✓ Correct Answer: C. Is of benefit in preventing exercise induced bronchial spasm