**Core Concept**
Magnesium and aluminium hydroxide combination antacids work by neutralizing stomach acid and providing rapid symptomatic relief from heartburn and acid reflux. The combination of these two agents enhances the efficacy and reduces the side effects of individual components.

**Why the Correct Answer is Right**
Magnesium hydroxide has a rapid onset of action, providing quick relief from heartburn symptoms. Aluminium hydroxide, on the other hand, has a longer duration of action, which helps in sustained acid neutralization. The combination of these two agents takes advantage of their complementary properties, offering superior therapeutic effects. The synergistic action of magnesium and aluminium hydroxide helps in reducing the dose of each component, minimizing side effects such as diarrhoea (magnesium) and constipation (aluminium).

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify any advantage of the combination over individual components.
**Option B:** This option is incorrect because it suggests that the combination is used to reduce side effects, which is not the primary reason for using a combination antacid.
**Option C:** This option is incorrect because it implies that the combination is used to enhance the duration of action, which is not the primary advantage of using a combination antacid.

**Clinical Pearl / High-Yield Fact**
When using combination antacids, remember that magnesium hydroxide has a rapid onset of action, while aluminium hydroxide has a longer duration of action. This knowledge can help you choose the right antacid for a specific clinical scenario.

**Correct Answer: C. Enhanced efficacy through synergistic action.**