Concept:The question tests spelling errors. One option has an incorrect spelling compared to the standard dictionary form.Explanation:The misspelled word is "Idiosyncracy" (option A).Its correct spelling is "idiosyncrasy"."Idiosyncrasy" means a unique behavior or habit of a person.The other options "incredible" and "guidance" are spelled correctly.Thus, the error is in option A.Answer:Option A: Idiosyncracy (correct spelling: idiosyncrasy)