Final answer:
Professor Quirrell took a sabbatical after teaching Muggle Studies and before his role as the Defense Against the Dark Arts teacher, during which he encountered Voldemort.
Step-by-step explanation:
The character Professor Quirrell, who appears in the Harry Potter series, is known to have taken a year-long sabbatical prior to teaching Defense Against the Dark Arts (DADA) at Hogwarts. According to the backstory provided by J.K. Rowling, Quirrell was originally a teacher of Muggle Studies before deciding to gain first-hand experience. During this time away, he encountered Voldemort in an unfortunate turn of events, ultimately leading to his possession by the Dark Lord, who was seeking a way to regain a body and return to power.
The correct answer to the question is Option 1: He went on a sabbatical. This term refers to a period of leave typically taken by an academic to study or travel, which aligns with Quirrell's desire to seek out new experiences and challenges that he had not encountered within the confines of his previous Muggle Studies position.