## Core Concept
The combination of magnesium and aluminium salts in antacids leverages the benefits of both components to neutralize stomach acid effectively. Magnesium salts tend to act quickly but have a shorter duration of action, while aluminium salts have a slower onset but longer-lasting effects.

## Why the Correct Answer is Right
The combination of magnesium and aluminium salts in antacids provides a balanced effect, offering both rapid and sustained neutralization of gastric acid. Magnesium hydroxide acts quickly to neutralize acid, providing immediate relief, whereas aluminium hydroxide has a slower onset of action but provides longer-lasting relief. This combination helps to mitigate the side effects associated with high doses of either component, such as diarrhoea with magnesium and constipation with aluminium.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is not provided, but typically, incorrect options might suggest reasons such as cost-effectiveness, increased shelf life, or enhanced absorption of other nutrients, which are not directly relevant to the primary benefit of combining magnesium and aluminium salts in antacids.
- **Option B:** Similarly, without the specific text, we can infer that any option not highlighting the balanced effect and side effect profile would be incorrect.
- **Option D:** This option is also not provided, but any choice not addressing the therapeutic benefits of the combination would be incorrect.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the combination of magnesium and aluminium salts in antacids helps to balance the gastrointestinal side effects. Magnesium can cause diarrhoea, while aluminium can cause constipation. Their combination tends to minimize these side effects, making the antacid more tolerable for patients.

## Correct Answer: C.