**Core Concept**
Secondary prevention aims to detect and treat conditions at an early stage, before symptoms appear, to prevent the progression of disease and reduce the risk of complications. This approach focuses on identifying asymptomatic individuals who are at high risk of developing a specific disease or condition.

**Why the Correct Answer is Right**
Secondary prevention typically involves screening tests, such as mammography for breast cancer or colonoscopy for colorectal cancer, to identify individuals with preclinical disease. Early detection and intervention can prevent the development of overt symptoms and reduce the risk of disease progression. For example, screening for hypertension can help prevent the development of cardiovascular disease by identifying individuals with high blood pressure and initiating treatment to lower their blood pressure.

**Why Each Wrong Option is Incorrect**
**Option A:** Primary prevention is the correct answer for this question. Primary prevention aims to prevent the occurrence of disease by eliminating or reducing risk factors. This includes measures such as vaccination, healthy diet, and regular exercise.
**Option B:** Tertiary prevention is a type of prevention that focuses on managing and rehabilitating individuals who already have an established disease or condition. This approach aims to prevent further deterioration and improve the quality of life for individuals with chronic diseases.
**Option C:** Primordial prevention is a type of prevention that aims to prevent the emergence of risk factors in a population. This approach focuses on promoting healthy lifestyles and behaviors to prevent the development of disease.

**Clinical Pearl / High-Yield Fact**
It's essential to remember the three levels of prevention: primary, secondary, and tertiary. Primary prevention aims to prevent disease, secondary prevention aims to detect and treat disease early, and tertiary prevention aims to manage and rehabilitate individuals with established disease.

**Correct Answer: D. Secondary prevention is applicable to detecting and treating conditions at an early stage, before symptoms appear.**