What’s the problem that you need help in
Noun-word that functions the same thing/set of things (person, place, or thing)
pronoun-word that substitute for a noun
I'll help as soon as I can but what's this question referring to? A book or?
The correct answer is reflexive.
Reflexive pronouns are used when the object of the sentence is the same person as the subject. Here, the subject is Johnny and given that he bought something for himself, he is also the object. Although the pronoun himself can sometimes be intensive, this is not the case where it is. Intensive pronoun would be if the sentence said: Johnny himself bought a new basketball.
