**Core Concept**
The question is testing the student's knowledge on the pharmacological management of coronary artery disease (CAD), specifically secondary prevention. Secondary prevention aims to reduce the risk of future cardiovascular events in patients with established CAD. The underlying principle is the use of medications to modify the underlying pathophysiology of atherosclerosis and reduce cardiac morbidity and mortality.

**Why the Correct Answer is Right**
The correct answer is a statin, which is a HMG-CoA reductase inhibitor. Statins work by inhibiting the enzyme HMG-CoA reductase, which plays a crucial role in cholesterol synthesis in the liver. By reducing cholesterol production, statins lower the levels of low-density lipoprotein (LDL) cholesterol, also known as "bad" cholesterol, in the blood. This is essential for secondary prevention of CAD, as high levels of LDL cholesterol contribute to the progression of atherosclerosis and increase the risk of cardiovascular events. Statins also have pleiotropic effects, including anti-inflammatory and antioxidant properties, which further contribute to their cardiovascular benefits.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because beta-blockers, while useful in the acute management of myocardial infarction and in managing heart failure, do not have a primary role in secondary prevention of CAD.
* **Option B:** This option is incorrect because calcium channel blockers are primarily used to manage hypertension and angina, and are not a first-line agent for secondary prevention of CAD.
* **Option D:** This option is incorrect because ACE inhibitors are primarily used to manage heart failure and hypertension, and are not a first-line agent for secondary prevention of CAD.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that statins are not only effective in lowering LDL cholesterol but also have pleiotropic effects that contribute to their cardiovascular benefits. This makes them a cornerstone of secondary prevention of CAD.

**Correct Answer:** C. Statins