Mary, a veterinary student, has been assigned an experiment in mammalian physiology that would require her to take a healthy, anesthetized dog and subject it to a drastic blood loss in order to observe the physiological consequences of shock. The dog would neither regain consciousness nor survive the experiment. Mary decides not to do this assignment. Mary's decision most closely accords with which one of the following principles? ['The only sufficient justification for experimenting on animals is that future animal suffering is thereby prevented.', 'Practicing veterinarians have a professional obligation to strive to prevent the unnecessary death of an animal except in cases of severely ill or injured animals whose prospects for recovery are dim.', 'Taking the life of an animal is not justifiable unless doing so would immediately assist in saving several animal lives or in protecting the health of a person.', 'No one is ever justified in acting with the sole intention of causing the death of a living thing, be it animal or human.']