Which of these is the best source of stem cells and minimizes the risk associated with stem cell transplantation?
a) stem cells from a donor having the same blood group
b) stem cells from a donor who is the same age as the patient
c) stem cells preserved from the umbilical cord of the person
d) stem cells from rejected grafts that initiated an immune response
d) reusing the trees creates less environmental waste.

The statement "The stem cells preserved from the umbilical cord of the person" is the BEST source of stem cells and minimizes the risk associated with stem cell transplantation.

Explanation:

On late back before 90s people use to throw away the umbilical cord as well as the blood because they believed it as a medical waste. But, in today's generation parents are found to be storing safely their baby's umbilical cord  and the blood as it has the stem cells which can be used against the treatment of various life-threatening and debilitating diseases. It has also shown the visible results in the treatment.

rain is the best answer

metamorphism is the change of minerals or geologic texture (distinct arrangement of minerals) in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change). the change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. i hoped i !