**Core Concept**
The liver after transplant enlargement is a common phenomenon due to various factors including drug-induced hepatotoxicity, viral hepatitis, and immunosuppressive regimen-related changes.

**Why the Correct Answer is Right**
The liver enlargement in the transplant setting is often attributed to the effects of immunosuppressive drugs, particularly corticosteroids and calcineurin inhibitors like tacrolimus and cyclosporine. These medications can cause hepatomegaly by promoting cellular growth and inhibiting apoptosis. Additionally, viral hepatitis and drug-induced liver injury can also contribute to liver enlargement in transplant patients.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide a valid reason for liver enlargement in transplant patients.
**Option B:** This option is incorrect because it is not a known cause of liver enlargement in transplant patients.
**Option C:** This option is incorrect because it is a potential cause of liver enlargement, but not the most common one.

**Clinical Pearl / High-Yield Fact**
It is essential to monitor liver function tests and imaging studies in transplant patients to detect early signs of liver enlargement, which can be a precursor to more severe complications like graft dysfunction.

**Correct Answer:** C.