**Core Concept**
The concept being tested here is the classification of vaccines based on their preparation method and the type of immune response they elicit. Killed vaccines, also known as inactivated vaccines, contain a pathogen that has been killed or inactivated, and they are unable to cause the disease they are intended to prevent.

**Why the Correct Answer is Right**
The correct answer is related to the mechanism of action of killed vaccines. These vaccines prepare the body's immune system to recognize and respond to specific pathogens by presenting antigens to the immune system without causing the disease itself. Killed vaccines induce an immune response through the activation of antigen-presenting cells, such as dendritic cells, which then present antigens to T-cells and B-cells, leading to the production of antibodies and the development of immune memory.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it refers to a different type of vaccine. Live, attenuated vaccines, on the other hand, contain a weakened or attenuated form of the pathogen and can cause a mild form of the disease they are intended to prevent.
* **Option B:** This option is incorrect because it refers to a different type of vaccine. Subunit vaccines contain only specific components of the pathogen, such as proteins or polysaccharides, and do not contain the entire pathogen.
* **Option C:** This option is incorrect because it refers to a different type of vaccine. Conjugate vaccines are a type of subunit vaccine that combines a polysaccharide antigen with a protein carrier to enhance the immune response.

**Clinical Pearl / High-Yield Fact**
It is essential to understand the different types of vaccines and their mechanisms of action to choose the most appropriate vaccine for a specific disease or population. Killed vaccines are often used for diseases such as influenza and hepatitis A, while live, attenuated vaccines are used for diseases such as measles and mumps.

**Correct Answer: C.**