**Core Concept**
Graft-Versus-Host Disease (GVHD) is a major complication of allogeneic hematopoietic stem cell transplantation, where immune cells from the donor (the graft) recognize the recipient (the host) as foreign and mount an immune response. This reaction involves **T lymphocytes** and can affect multiple organs. The primary sites of involvement include the skin, liver, and gastrointestinal tract.

**Why the Correct Answer is Right**
The correct answer is not provided, however, in GVHD, the skin, liver, and gastrointestinal tract are commonly affected. The **skin** is the most frequently involved organ, with symptoms ranging from a mild rash to severe blistering. The **liver** can show signs of dysfunction, including elevated liver enzymes and bilirubin levels. The **gastrointestinal tract** can exhibit symptoms such as diarrhea, abdominal pain, and nausea.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option text, it's challenging to provide a detailed explanation. However, if an option suggests an organ not typically involved in GVHD, it would be incorrect.
**Option B:** Similarly, without the specific text, it's difficult to comment. If it mentions an organ or system rarely affected in GVHD, it would not be the correct answer.
**Option C:** If this option suggests that only one or two of the commonly affected organs are involved, it underrepresents the scope of GVHD.
**Option D:** If it proposes an organ or system not typically associated with GVHD, it would be an incorrect choice.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that GVHD can be acute or chronic, with different timelines and symptom profiles. Recognizing the organs commonly affected and the distinction between acute and chronic GVHD is crucial for diagnosis and management.

**Correct Answer:** Not provided in the query.