Southington University's fund-raisers succeeded in getting donations from 80 percent of the potential donors they contacted this year. This rate would be the expected rate if the only potential donors contacted were those who have donated in the past. But good fund-raisers constantly contact less likely prospects in an effort to expand the donor base. Thus the high success rate, far from showing that the fund-raisers did a good job, shows insufficient canvassing effort.
Which of the following, if true, most seriously weakens the argument?
【选项】Among potential donors contacted by Southington University's fund-raiser,the majority of those who did not make donations were people who had made donations to the university in the past.