Despite being in an irreversible coma, Karen Ann Quinlan was not considered to be totally brain dead because

a. it was likely that she would regain consciousness at some time in the future.
b. she continued to show significant activity in her cerebral cortex.
c. her condition was due to an environmental accident (drug use), not a natural biological process (e.g., cancer).
d. her brain stem was still functioning enough to support breathing and some other body functions.

d