Stem cells are being used to treat many conditions, including spinal cord injuries and macular degeneration. However, using stem cells raises some ethical questions. Why are there ethical concerns with using stem cells?

A.Harvesting embryonic stem cells often results in destruction of an embryo.
B.Adult stem cells are often harvested without consent from patients in hospitals.
C.Induced pluripotent stem cells are not as powerful totipotent stem cells.
D.Adult stem cells often cause premature aging when injected into younger patients.