Which of the following is a benefit of using adult stem cells?

Using adult stem cells has the significant benefit of being less likely to be rejected by the patient's body. This is largely because adult stem cells can be harvested from the patient themselves, which means that they are genetically identical to the recipient's cells. The immune system would recognize these cells as "self" and would not mount an attack against them. This contrasts with cells from other sources, such as embryonic stem cells, where the immune system may recognize them as foreign.

The other options highlight limitations or concerns associated with stem cell therapies that do not apply to adult stem cells in the same way. For example, the ethical concerns are more pronounced with embryonic stem cells rather than adult stem cells, which are generally considered ethically acceptable since they do not involve the destruction of embryos. Additionally, while adult stem cells offer some availability, they are not considered to provide an unlimited supply compared to other types of stem cells, such as those sourced from embryos or pluripotent stem cells. Therefore, the key advantage of using adult stem cells lies in their compatibility with the patient's immune system, minimizing the risk of rejection.