Holden has many questions in the Catcher in the Rye, most of his anxiety stems from his inability to get an answer to the question, why his little brother had to die at such a young age. Holden experiences a deep sense of grief, most of which is too painful to confront and gets suppressed which causes Holden to experience depression.
Holden questions how his parents can go on with their lives when they lost a son. How can people just move past such a momentous loss and go to work and continue as before, when nothing will ever be the same? This offends Holden and he fears and resents his parents, and fails to communicate with them which is part of his problem.
Another question that Holden asks has to do with where the ducks go, the ducks who live in the pond in Central Park, Holden is confused about the cycle that the ducks engage in every year. This question is also connected to his attempt to understand life and death. The ducks come back and this is a comfort to Holden.
Holden questions why all adults are phony, he rejects adult behavior as insincere and therefore does not want to become an adult.
Holden also grills Stradlater about his date with Jane Gallagher, asking him over and over, "does she still keep her kings in the back row," a reference to Jane's sexual purity that Holden remembers from their days together in Maine.
While Sally Hayes is questioning Holden about whether he will come over to her house on Christmas Eve to help decorate the tree, he is thinking more philosophically. He asks her:
"Did you ever get fed up I mean did you ever get scared that everything was going to go lousy unless you did something? I mean do you like school and all that stuff?" (Salinger)