**Core Concept**
Hyperacute rejection is an immediate and severe form of graft rejection that occurs within minutes to hours after transplantation. It is primarily caused by pre-existing antibodies against the donor's human leukocyte antigens (HLA) or other antigens present on the graft.

**Why the Correct Answer is Right**
Hyperacute rejection is most commonly seen in kidney transplants, as the kidneys have a rich blood supply that allows the immune system to quickly identify and respond to the transplanted organ. The presence of pre-existing antibodies against the donor's HLA or other antigens triggers an immediate and severe immune response, leading to the activation of complement and the formation of thrombi, which cause the graft to fail. The high blood flow to the kidneys also facilitates the rapid accumulation of immune complexes and the activation of the coagulation cascade.

**Why Each Wrong Option is Incorrect**
**Option A:** While liver transplants can also experience hyperacute rejection, it is less common due to the liver's unique ability to regenerate and the lower level of HLA expression on its cells. However, the liver is still a potential site for hyperacute rejection.
**Option B:** Hyperacute rejection is not typically seen in heart transplants, as the heart has a lower level of HLA expression and the immune response is slower to develop.
**Option C:** Pancreas transplants can experience hyperacute rejection, but it is less common than in kidney transplants due to the lower level of HLA expression on pancreatic islet cells.

**Clinical Pearl / High-Yield Fact**
The Banff classification criteria for hyperacute rejection include the presence of thrombi, interstitial hemorrhage, and the activation of complement on the graft's endothelial cells.

**Correct Answer: D. Kidney.**