The Phenomenon of Apoptosis or Cell Death, as It Relates

The phenomenon of apoptosis or cell death, as it relates to morphogenesis in Drosphila melanogaster,

A) is a mechanism present in every cell that occurs when an inhibitory protein is inactivated.
B) occurs when the cellular machinery simply wears out and the cell dies from being unable to continue vital processes.
C) occurs when the ability of the cell to repair DNA mutations finally fails.
D) is a disease phenomenon and cell death is always a bad trait.
E) is not yet understood but probably involves the failure of the homeobox to correctly control development.