It's purpose is to promote the "Make A Difference Day" program which encourages people to make a difference, together! It has been used as a tool to make announcement, create instructions, promote awareness and calls for an action to be done in relation to the programs vision.
He tells Percy the story about the tree and a girl named Thalia. The story was that Thalia, Annabeth and other half bloods where exploring outside of the half blood camp. But then monsters came out of nowhere and started fighting them. They tried to fight the monsters but they weren’t strong enough. So Thalia protected them and risked her own life to save them. But thalia died and Zeus her father grew a tree in her honor, and the tree provided a barrier for the camp to keep them safe. :-)
The correct answer is The alligator slipped quietly into the water.
The first sentence does not agree since alligators should be a singular form, while the second and third are nonsensical because of lack of information.