GWD7-8，很挣扎。。。求解答

橙色的鱼

For many years, theoretical economists characterized humans as rational beings relentlessly bent on maximizing purely selfish reward. Results of an experimental economics study appear to contradict this view, however.  In the “Ultimatum Game,” two subjects, who cannot exchange information, are placed in separate rooms.  One is randomly chosen to propose how a sum of money, known to both, should be shared between them; only one offer, which must be accepted or rejected without negotiation, is allowed.
     If, in fact, people are selfish and rational, then the proposer should offer the smallest possible share, while the responder should accept any offer, (20) no matter how small:  after all, even one dollar is better than nothing.  In numerous trials, however, two-thirds of the offers made were between 40 and 50 percent; only 4 percent were less than 20 percent.  Among responders, more than half who were offered less than 20 percent rejected the offer.  Behavior in the game did not appreciably depend on the players’ sex, age, or education.  Nor did the amount of money involved play a significant role:  for instance, in trials of the game that were conducted in Indonesia, the sum to be shared was as much as three times the subjects’ average monthly income, and still responders refused offers that they deemed too small.
Q8:
The author refers to the sum of one dollar (line 21) in order to

A.    question the notion that the amount of money involved significantly affected players’ behavior
B.    provide an example of one of the rare offers made by proposers that was less than 20 percent
C.    ！illustrate the rationality of accepting even a very small offer
答案是C，ONE DOLLAR的例子提到虽然数额很大但RESPONDER仍然会拒绝接受这个明显和RATIONAL矛盾了，所以个人就没有选C选的是A,因为A正好与前面说behavior not depend on amount of money 相呼应。。。很纠结，想了很久都没头绪，求童鞋解答

橙色的鱼

呼唤。。。