Which best describes stem cells?
a) differentiation creates specialized cells from stem cells.
b) self-renewal creates stem cells from differentiated cells.
c) self-renewal creates differentiated cells from stem cells.
d) differentiation creates stem cells from specialized cells.

The correct option is A.

STEM cells are those cells which are undifferentiated and they have the capacity to reproduce themselves by means of self renewal; they do this by differentiating into different cell types from which can be formed highly differentiated cells. New scientific knowledge that have been made available through STEM cell biology are now been used in diverse ways including developing treatment for various reproductive diseases.