The question says, "A group of closely associated colleagues has made a disastrous diplomatic decision after a series of meetings marked by disagreement over conflicting alternatives. It can be inferred from the passage that the author would be most likely to say that this scenario..."
(C) says, "provides no evidence that groupthink played a role in the group’s decision"
We know the people are closely associated and colleagues with one another. They're debating alternative decisions. From this, we can infer that the people in this group are cohesive, as this type of blatant disagreement does not occur in groups that are not cohesive (lines 5-7). What else can we figure out about this group? Did they act in a groupthink-like manner? We know from the passage that groupthink happens when people aren't critical about group proposals and don't raise their objections to them (lines 21-31). However, this doesn't look to be the case with this group, as the group had heated debates. Additionally, in looking at the author factors of groupthink mentioned by the researchers in lines 40-52 (including overestimating the group's correctness, closed-mindedness to alternative ideas, and strong pressure to conform to the consensus), we have no evidence that the group described in the stimulus is exhibiting any of these characteristics. Thus, (C) says what the author would likely think about this group—there's no evidence that they're committing groupthink.
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