Southington University's fund-raisers succeeded in getting donations

Fund-raisers got donations from 80% of people they contacted. (So they contacted 100 people and asked them for donation - 80 agreed. We don't know who these 100 people were - how many were new/ how many were old - not known)
80% is the expected conversion rate if only past donors are contacted.
But good fund-raisers contact less likely prospects (new) to expand the donor base.

Conclusion: High success rate shows insufficient canvassing effort. It seems that the fund raisers contacted only old donors and didn't try to expand the donor base.

The argument is trying to tell us that the 80% conversion rate shows that the fund-raisers contacted only old donors and did not try to expand donor base. So they lacked in effort.

We need to weaken the argument - so we need an option that tells us something like they did contact new potential donors too and were successful in getting them onboard.

(A) Among potential donors contacted by Southington University's fund-raisers, the majority of those who did not make donations were people who had made donations to the university in the past.

Of the 100, 80 made donations and 20 did not. Of these 20, majority were old donors so say 15 were old donors. This just works well with our conclusion that the fund raisers contacted only the old donors. It doesn't weaken our conclusion.

(B) The amount of money raised by Southington University's fundraisers this year was lower than the amount they had raised in any of the previous several years.

Our argument talks about canvassing effort (how many and which people were contacted) and conversion rate of effort. Amount of money raised is not relevant.

(C) Individual donations made to Southington University this year were, on average, slightly larger than were average individual donations made to many other universities.

Again, size of donations is irrelevant. Donor base needed to be expanded.

(D) Fund-raisers contacting past donors are not only to get new donations but also to get names of potential new donors to contact.

Irrelevant how the potential new donor names are obtained.

(E) The majority of the donations that fund-raisers succeeded in getting for Southington University were from who had never given to the university before.

So of the 80 people who donated, more than 40 were new donors. So new donors were contacted and donor base was increased. Hence, there may not have been a lack of effort. This weakens the conclusion.

Answer (E)