How is substituted consent defined?

How is substituted consent defined?
 A) The administrator of the healthcare facility is constitutionally permitted to sign the consent to treatment for a mentally incompetent patient.
  B) A healthcare provider continues with life-saving measures after a competent adult refuses to provide consent even when in his best interest.
  C) A healthcare provider can provide treatment to the patient when the patient cannot provide consent to treatment and an authorized individual provides consent.
  D) Another adult may provide consent that is in the best interest of another competent adult who is refusing a life-saving treatment.