"Letting Die" Is Prima Facie Acceptable in Medicine Under Which

"Letting die" is prima facie acceptable in medicine under which of the following conditions?

A) The physician has determined that the social worth of the patient is no longer high enough to justify treatment.
B) Either the patient or his or her authorized surrogates have validly refused a medical technology.
C) A medical technology is useless, in the strict sense of medical futility.
D) All of the above
E) Both B and C