Which of these is the BEST source of stem cells and minimizes the risk associated with stem cell transplantation?(Please Help!!)

Select one:
a. Stem cells from rejected grafts that initiated an immune response.
b. Stem cells preserved from the umbilical cord of the person.
c. Stem cells from a donor having the same blood group.
d. Stem cells from a donor who is the same age as the patient.

Juan and carol were studying invertebrates in biology. they knew that segmented or earth worms preferred a dark, moist habitat. during this lab, they would be investigating the responses of organisms called planaria or dugesia tigrina. these were simple flatworms that still had a one-way digestive system and a very simple nervous system. juan and carol placed the planaria in a petri dish containing cool, distilled water that was partially covered with black paper. they shined a light on the dish. next, they removed the paper and placed a small amount of chicken liver at one end of the dish. they added a few large salt crystals to the water. finally, they added drops of hot water to the cool water in the petri dish. their results can be seen in the data table. according to their experiment, all but one conclusion is valid.