Why Would It Be Helpful to Be Able to Generate

Why would it be helpful to be able to generate blood cells from stem cells?

A) Donated blood is often contaminated.
B) Blood donors would no longer be needed.
C) Mainly, as a step along the way toward learning how to generate more useful cells
D) There are not enough blood and bone marrow donors to meet the need.
E) It would cost less than using people as donors.