**Core Concept**
Tertiary level prevention refers to the prevention of disease progression and the management of complications in individuals with established disease. This level of prevention aims to reduce the impact of an ongoing illness that has already developed, such as managing diabetes to prevent complications.

**Why the Correct Answer is Right**
Tertiary level prevention typically involves interventions that are specifically targeted at individuals with a diagnosed condition, such as surgery, rehabilitation, and management of chronic diseases. These interventions aim to reduce the severity and impact of the disease, improve quality of life, and prevent further complications.

**Why Each Wrong Option is Incorrect**
* **Option A:** Primary prevention refers to the prevention of disease before it occurs, such as vaccination and health education. This is not a form of tertiary level prevention.
* **Option B:** Secondary prevention involves the early detection and treatment of disease to prevent its progression, such as cancer screening and blood pressure monitoring. This is not a form of tertiary level prevention.
* **Option C:** Tertiary level prevention is focused on managing established disease, but it can also include some aspects of secondary prevention, such as disease monitoring and early intervention. However, without more context, this option is ambiguous and may not clearly represent a form of tertiary level prevention.

**Clinical Pearl / High-Yield Fact**
It's essential to understand the three levels of prevention: primary, secondary, and tertiary. Primary prevention aims to prevent disease before it occurs, secondary prevention focuses on early detection and treatment, and tertiary prevention involves managing established disease to prevent further complications.

**Correct Answer: A. Primary prevention**