To face danger solely because doing so affords one a certain pleasure

let us simplify the argument given --

1. Facing danger ONLY BECAUSE it affords a certain pleasure --> not Courage -------------(1)

2. Real Courage --> In attaining a goal, a person perseveres in the face of fear prompted by one or more dangers involved -----------(2)

let us look at the answer options now --

Option A - Incorrect

We cannot infer anything about situations that involve "future pain". What if in such a situation, the person perseveres in the face of fear? Then he/she would indeed be courageous according to point #2.

Option B - Incorrect

But what if the person does indeed persevere in face of those one or more dangers? Then he/she would indeed be courageous according to point #2.

Option C - Incorrect

This is an incorrect reading of point #1. If the person faces danger ONLY for pleasure, then he/she cannot be called courageous.
In this case, what if the person ALSO perseveres in the face of fear prompted? That person would then be courageous.

Option D - Correct

This option reads --

A person who faces danger in order to benefit others is acting courageously --> Afraid of the danger

This is more or less, a restatement of point #2. Let us read point #2 carefully. Point #2 talks about courage in ANY situation. The necessary condition involves two things -- 1. fear of the danger 2. perseverance in the face of such fear.

Hence, "afraid of the danger" has to be A necessary condition, the other being "perseverance in the face of such fear". This is true because WITHOUT being afraid of the danger, there is no real courage.

Option E - Incorrect

"cannot be said to be courageous in any situation" -- too extreme. What if the person fears some situations that others do not fear and perseveres? He would then be said to be courageous in THOSE situations.