Laurel: Modern moral theories must be jettisoned, or at least greatly reworked, because they fail to provide guidance in extreme cases, which are precisely the times when people most need guidance.
Miriam: A moral theory, like an overcoat, can be quite useful even if it is not useful in every possible situation. Being useful in a wide variety of common circumstances is all we need from a moral theory.
Laurel's and Miriam's statements provide the most support for the claim that they disagree about whetherLaurel thinks a moral theory is seriously inadequate if it fails in extreme cases. Miriam thinks a moral theory can still be adequate if it works well in many ordinary cases. So their disagreement is about
whether usefulness in extreme cases is required for a moral theory to be acceptable.
(A) it is preferable to develop a moral theory that provides solutions to all the moral dilemmas that could arise
This is too broad. Laurel talks about extreme cases, not necessarily every possible moral dilemma.
(B) people abandoned earlier moral theories when they encountered dilemmas that those theories did not adequately address
This is historical, and neither speaker discusses what people did with earlier theories.
(C) a moral theory's adequacy depends on its ability to provide guidance in extreme cases
This is correct. Laurel says failure in extreme cases is a reason to reject or greatly rework modern moral theories. Miriam says usefulness in common cases is enough, even if the theory is not useful in every situation. This is exactly the point of disagreement.
(D) just as people need different overcoats in different climates, so too do they need different moral theories on different occasions
This distorts Miriam’s analogy. She uses the overcoat example only to show that something can be useful without being useful
in every possible situation.
(E) a moral theory developed in the light of extreme cases is unlikely to provide adequate guidance in more usual cases
Neither speaker makes this claim. Miriam does not say extreme-case-based theories fail in ordinary cases.
Answer: (C)