Here we have a Strengthen with Necessary Premise question. Remember that a premise is necessary for a conclusion if the falsity of the premise guarantees or brings about the falsity of the conclusion. First we check to see if the answer choice strengthens the passage, and then, if it does strengthen, we negate the answer choice to see if its negation makes the argument fall apart. If the answer choice does both those things then it is our correct answer.
Here we are presented with an argument. Since our technique is to first find the answer choice that strengthens, a Strengthen with Necessary Premise question must always be an argument. You can't strengthen a set of facts; what would you be strengthening?
The conclusion of this argument is the first sentence, i.e. "The mark of a superior conductor is that he or she has the authority to insist, even with a top orchestra, that rehearsal must be intensified." Why? We know that this authority cannot be claimed. It must be earned through the conductor winning the respect of the orchestra for the artistic interpretations he or she is currently pursuing.
(A) is incorrect because it does not strengthen the argument. Whether or not a superior conductor devises different interpretations of a composition for each orchestra with which they perform has no relevance to our argument. It neither strengthens nor weakens it.
(B) is incorrect because it does not strengthen the argument. It doesn't matter whether the superior conductor is satisfied with the performance. We are concerned with the conductor first winning the respect of the orchestra for the artistic interpretations he or she is currently pursuing so that he or she can then earn the authority to insist that rehearsal work must be intensified, therein, showing his or her mark of being a superior conductor.
(C) is incorrect because it actually somewhat weakens the argument. If it were true that when the conductor considers additional rehearsing necessary, top orchestras are always ready to put in additional work on rehearsals, that would imply that first earning the orchestras respect will not be needed to insist on more rehearsing.
(D) is CORRECT because it strengthens the argument. If top orchestras can appreciate the merits of an interpretation even before they have brought it to full realization, then the conductor will be able to earn their authority by winning the orchestra's respect for the artistic interpretations he or she is currently pursuing. Basically, answer choice (D) is saying that winning the orchestra's respect in the manner specified (through the artistic interpretations he or she is currently pursuing) is possible. Now, let's negate: "Top orchestras cannot appreciate the merits of an interpretation before they have brought it to full realization." This makes the entire argument fall apart. If top orchestras cannot appreciate the merits of an interpretation before they have been brought to full realization (i.e. during rehearsal and times prior to the actual performance/perfection of it), then the conductor cannot win the orchestra's respect for the artistic interpretations he or she is currently pursuing. Thus, the conductor will not be able to earn the orchestra's respect, therein not being able to have the authority to insist that rehearsal work must be intensified.
(E) is incorrect because it is irrelevant. We are concerned with the mark of a superior conductor, not with those orchestras led by non-superior conductors.
Hope that was helpful! Please let us know if you have any other questions.
