This question seems to be incomplete. However, there is enough information to find the right answer.
Answer:
Holden says that, while shooting the bull, he was thinking about the ducks of a lagoon in Central Park, and what happens to them if the lagoon gets frozen.
Step-by-step explanation:
In the second chapter of J.D. Salinger´s "The Catcher in the Rye", Holden says that, while shooting the bull, he was thinking about the lagoon in Central Park, New York, where he lived. He found himself wondering if the lagoon would be frozen over when he got home, and what happens to the ducks if that happens.