What is a stem cell?
A "blank" or undifferentiated cell that can develop into different tissues.
A cell found in the stem of a plant.
A cell found at the base of an organ.

	Is there a difference between an adult and an embryonic stem cell?
An adult stem cell is older than an embryonic stem cell.
An embryonic stem cell is crankier than an adult stem cell.
There isn't a difference in an adult and embryonic stem cell.

	How can it repair a heart?
Stem cells digest or remove the damaged portion of the heart.
Stem cells make good mechanics.
Under the right conditions, stem cells can multiply and transform themselves into heart muscle cells and migrate into the damaged area.

	Why is using adult stem cells revolutionary?
For a long time, scientists only thought embryonic stem cells would regenerate into different tissue types.
Adult stem cells can be harvested and used from the same person, reducing many risks.
Both a) and b).