麻烦了

kun861010

Smithtown University’s fund-raisers succeeded in getting donations from 80 percent of the potential donors they contacted.  This success rate, exceptionally high for university fund-raisers, does not indicate that they were doing a good job.  On the contrary, since the people most likely to donate are those who have donated in the past, good fund-raisers constantly try less-likely prospects in an effort to expand the donor base.  The high success rate shows insufficient canvassing effort.



Which of the following, if true, provides more support for the argument?



a..Smithtown University’s fund-raisers were successful in their contacts with potential donors who had never given before about as frequently as were fund-raisers for other universities in their contacts with such people.

b..This year the average size of the donations to Smithtown University from new donors when the university’s fund-raisers had contacted was larger than the average size of donations from donors who had given to the university before.

c..This year most of the donations that came to Smithtown University from people who had previously donated to it were made without the university’s fund-raisers having made any contact with the donors.

d..The majority of the donations that fund-raisers succeeded in getting for Smithtown University this year were from donors who had never given to the university before.

e..More than half of the money raised by Smithtown University’s fund-raisers came from donors who had never previously donated to the university.

为什么a是正确的？我都没看懂a这句话的意思。为什么c不正确呢？