**Core Concept:** The immune system plays a crucial role in defending the body against pathogens, including viruses. One of its key components is the complement system, which is a group of proteins that work together to destroy pathogens, recruit immune cells, and promote inflammation.

**Why the Correct Answer is Right:** Complement system is a crucial component of the innate immune response. When activated, it forms a membrane attack complex (MAC) that creates pores on the surface of the pathogen, leading to cell lysis and death. This is the case for option C, which refers to the activation of complement system and its subsequent formation of MAC on the virus-infected cell, resulting in cell death.

**Why Each Wrong Option is Incorrect:**

A. Inhibition of virus replication (antiviral drugs) is not directly linked to killing of virus-infected cells. These drugs aim to decrease the number of virus particles produced by the infected cell, but do not directly cause the death of the cell itself.

B. Immune cells like macrophages and neutrophils engulf and destroy pathogens, but they do not directly kill virus-infected cells. Killing of virus-infected cells is a feature of the complement system.

D. Antibodies (IgG, IgA, IgM) are immune molecules that neutralize viruses, mark them for phagocytosis, and activate the complement system. However, they do not directly kill virus-infected cells.

**Clinical Pearl:** Understanding the complement system's role in destroying virus-infected cells is crucial for understanding the functioning of the immune system and treating viral infections. Complement system activation is often targeted in the treatment of viral diseases, as it contributes to the clearance of pathogens and prevention of their spread.

**Correct Answer:** C (Complement System activation leading to cell lysis via Membrane Attack Complex (MAC))