**Core Concept**
Autotransplantation involves transplanting tissue from one part of the body to another in the same individual, whereas isografts are transplants between genetically identical individuals, such as identical twins. However, when considering graft types, the primary distinction lies between autografts, allografts, isografts, and xenografts based on the genetic relationship between the donor and recipient.

**Why the Correct Answer is Right**
In this scenario, the ovary transplant is performed between genetically identical individuals, making it an isograft. Since the donor and recipient are identical twins, they share the same genetic makeup, which minimizes the risk of graft rejection. This type of graft is often used in transplant medicine when the donor and recipient are closely related and have a high degree of genetic similarity.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as autografts involve transplanting tissue from one part of the body to another in the same individual, which is not applicable in this scenario.

**Option B:** This option is incorrect as allografts involve transplanting tissue between genetically different individuals, which would increase the risk of graft rejection in this scenario.

**Option C:** This option is incorrect as xenografts involve transplanting tissue between different species, which is not relevant in this scenario.

**Clinical Pearl / High-Yield Fact**
Identical twins who are genetically identical can serve as ideal donors for organ transplants, such as isografts, minimizing the risk of graft rejection and improving patient outcomes.

**Correct Answer: D. Isograft.