Wow, a super difficult CR question!

John, an expert in game theory, predicts that negotiations cannot be resolved unless one party is willing to concede a symbolic step. He also believes that when a symbolic step of concession is taken, negotiations will be resolved. Other game theory experts, however, believe that these results do not take other variables into account.

Let's break this down:
John is an expert in game theory and makes a hypothesis that in order for negotiations to be resolved, one party must concede a symbolic step. That is, one side must show they are willing to cooperate by "giving up" something that is part of the negotiation; they need to symbolically take a step back. He also thinks that once a concession is made, the negotiations will inevitably be resolved.

Other experts contend however, that other variables (reasons) must be taken into account (before a prediction whether a negotiation will be successful or not).


John's hypothesis: symbolic step conceded by one party ---> negotiations will be resolved

Other's counter-argument: yes, but other variables are important too


Let's first go to the question to see what we are dealing with:
Which of the following, if true, best supports the contention in the last sentence?

Ok, we want to support the contention (argument) in the last sentence that there are other reasons for a negotiations success besides just one party making a symbolic concession.


Now let's go through the answer choices:

A. Predicting the success of a particular negotiation requires specifying the goal of the negotiation.
Trap answer. While this weakens John's argument, it does not support the idea that other factors are involved in the resolution of a negotiation very well. It just mentions one factor that could be involved in predicting if negotiations will be resolved.

B. Judging the outcome of a particular negotiation requires knowing about other negotiations that have taken place in the past.
This is just a fact about the field of game/negotiation theory. It tells us how the experts figure out things about the field and does not provide specific information to support the argument made by other experts.

C. Learning whether a certain negotiation strategy is good requires observing how that strategy works through several negotiating sessions.
Again, just a fact about the field.

D. Parties who are willing to take a symbolic step are more likely to complete negotiations successfully for other reasons.
This is the correct answer. It echos what the "other game theory experts" are saying. Yes, the symbolic step is important, but so are other reasons.

E. Making a negotiation successful requires knowing the context of symbolic steps that a party in the negotiations might desire.
Another trap answer. While knowing the context of the symbolic step, that is the situation in which the symbolic step occurs, could be helpful in determining the "other reasons" for why a negotiation will be successful, it does not give us much direct evidence to support the contention (argument) that there are other factors (variables) involved in predicting a successful negotiation.