Final answer:
Large non-profit hospitals' practice of acknowledging donors through walls of honor, galas, and plaques is an example of donor retention tactics.
Step-by-step explanation:
The activity of large non-profit hospitals listing donors on a wall and holding galas to give plaques and recognition is an example of donor retention tactics. Through these actions, the hospitals aim to appreciate the benefactors' contributions and incentivize them to continue their support. This strategy is effective in maintaining a steady flow of donations, crucial for the sustainability and progression of the hospitals' services and programs.