**Core Concept**
Screening programs aim to detect diseases at an early stage, often before symptoms appear, to reduce morbidity and mortality. Cost-effectiveness is a crucial factor in determining the most suitable screening method for a particular disease.

**Why the Correct Answer is Right**
The most cost-effective method of screening depends on the disease, its prevalence, and the availability of resources. However, in general, **mass screening** is considered the most cost-effective approach for diseases with high prevalence, such as hypertension or diabetes. Mass screening involves testing a large population, often through a simple, non-invasive method, to identify individuals at risk. This approach allows for early detection and intervention, reducing the burden of the disease on the healthcare system.

**Why Each Wrong Option is Incorrect**
* **Option A:** **Targeted screening** is more effective for diseases with low prevalence, such as certain genetic disorders. It involves testing a specific subgroup of the population, which may not be the most cost-effective approach for diseases with high prevalence.
* **Option B:** **Case-finding** is a more expensive approach that involves searching for individuals with a specific disease within the healthcare system. This method is often used for diseases with low prevalence, such as rare genetic disorders.
* **Option C:** **Risk factor assessment** is a cost-effective approach, but it is not as effective as mass screening for diseases with high prevalence. Risk factor assessment involves evaluating individual risk factors, such as family history or lifestyle, to identify individuals at risk.

**Clinical Pearl / High-Yield Fact**
When planning a screening program, consider the **3 A's of screening**: Acceptability, Accessibility, and Affordability. A screening program should be acceptable to the target population, accessible to those who need it, and affordable for the healthcare system.

**Correct Answer:** C.