Which of these is the BEST source of stem cells and minimizes the risk associated with stem cell transplantation?

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.

The images show two species of tree frogs in a particular region. the gray tree frogs are adapted to the trees of the woodlands, while the green tree frogs can survive in woodlands or grasslands. the gray frog was abundant in the woodlands. because of climatic changes, most of the trees in the region died, and the woodlands changed to grasslands. in such a case, the . the gray tree frog is closely related to the green tree frog genetically, but they have different mating calls. this suggests that speciation occurred because of .