Task 5 In an experiment designed to study the effect of majority opinion, small groups of subjects (实验对象) observed a standard straight line, and then judged which of three other lines equaled its length. One of the other lines was longer, one shorter, one equal to the standard; the differences were great enough that they could be told easily. All but one member of each group had been instructed to agree upon a wrong answer for a majority of the trials. The experimental subject was thus put against a majority, and the subject’s problem was whether to disagree with the majority, or to doubt his or her own judgment and agree. Many subjects refused to change and continued to hold to their independent ideas. But a rather large number of them yielded under pressure from other’s apparent judgments. The amount of yielding depended on the clarity of conditions (lack of clariw led to their following majority opinion) , individual differences, and the size of the opposition. With the opposition of only one other person, there was very little yielding; with two against one the amount of yielding became pronounced (显著的) ; and a majority of three was nearly as effective as larger majorities against the only one who disagreed. What does the passage mainly discuss
A．The accuracy of threshold judgment. B．The inability of groups to estimate correct line length. C．The impact of majority opinion on the judgment of an individual. D．The necessity of clear conditions in conducting successful experiments.