The concept of “concern for the consequences of actions” is irrelevant. The author’s assumption is that in order to desire to conform to a principle, one must have free will. Neither of these concepts requires a connection to being concerned about the consequences of actions. (Consequences may relate to the “moral worth,” as mentioned in the context. But that’s not part of the author’s reasoning.)

Necessary, because if this were not true — if desiring to conform to a principle does NOT require free will — then we have no reason to believe that being a moral agent requires free will. Another way to think about this answer is that it is the link the author needs to get from “desire to conform to a principle” to “free will” in the conclusion.

“Taking the consequences of an action into consideration” is irrelevant to the reasoning. The author’s assumption is that in order to desire to conform to a principle, one must have free will. Neither of these concepts requires a connection to taking into account consequences. (Consequences may relate to the “moral worth,” as mentioned in the context. But that’s not part of the author’s reasoning.)

(D) asserts that having desires requires being a moral agent. But that just twists the author’s premise, which is that being a moral agent requires desiring to conform to a principle. (D) isn’t necessary, because even if one could have desires without being a moral agent, that doesn’t relate to whether one needs to have the desire to conform to a principle in order to be a moral agent, or whether one needs free will in order to be a moral agent.

Not necessary, because the performance of morally worthy actions is irrelevant to the reasoning. The author’s assumption is that in order to desire to conform to a principle, one must have free will. Neither of these concepts requires a connection to morally worthy actions. (”Moral worth” may relate to the first sentence, which is context. But that’s not part of the author’s reasoning.)