**Core Concept**
Epstein-Barr virus (EBV) is a herpesvirus that primarily infects B lymphocytes and has been implicated in various autoimmune diseases. EBV triggers a persistent infection in host cells, leading to chronic antigenic stimulation and potential breakdown of immune tolerance.

**Why the Correct Answer is Right**
EBV causes autoimmunity by inducing molecular mimicry and epitope spreading. During EBV infection, the virus expresses proteins that share epitopes with host proteins, triggering an immune response against self-antigens. The virus also induces the expression of costimulatory molecules and cytokines, leading to chronic activation of B cells and T cells. This results in the formation of autoreactive immune cells and the development of autoimmune diseases, such as multiple sclerosis, lupus, and rheumatoid arthritis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because EBV does not primarily cause autoimmunity through viral oncogenesis, although it is a known risk factor for certain cancers, such as Burkitt lymphoma.
**Option B:** This option is incorrect because EBV does not primarily cause autoimmunity through direct cytotoxicity, although it can induce apoptosis in infected cells.
**Option C:** This option is incorrect because EBV does not primarily cause autoimmunity through impaired immune function, although it can modulate the host immune response.

**Clinical Pearl / High-Yield Fact**
EBV has been implicated in approximately 90% of the world's population, with most individuals becoming infected in childhood. Chronic EBV infection has been linked to various autoimmune diseases, emphasizing the importance of monitoring and managing EBV infection in patients with autoimmune disorders.

**Correct Answer:** C.