Throughout the novel, Salinger displays Holden's mental instability by utilizing many themes, such as the effects of alienation, the pain of maturation, and the superficiality of the adult world.
Welcome to the forum.
As you will see from the forum guidelines, we cannot help with homework, assignments, theses etc. It would be very unfair to get help with something that is going to be marked. They need to see what you can write on your own, without assistance.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.