Answer: The statement that requires a citation when used in a research paper is A. Lorne Falconi suggests that an existential angst hovers over Salinger's characters.
Step-by-step explanation: Citation is required when an author paraphrases or uses an idea that another author has already expressed in one of his/her texts. Statement A. is the one that requires citation as it makes reference to an idea or interpretation about Salinger's characters that has been developed by another author (Lorne Falconi). In other words, A. requires citation because it includes an idea that did not come out from the author's mind, but from another writer's mind.