According to Beauchamp and Childress, Why Have Some Philosophers Questioned

According to Beauchamp and Childress, why have some philosophers questioned the place of virtues in moral theory?

A) Virtues are thought to be meaningless for moral behavior.
B) Principles are thought to override questions of character in thinking about the moral life.
C) Virtues are thought to be less central than norms and difficult to unify in a systematic theory.
D) Emphasis on virtues is thought to ignore some participants in the moral life.