In Book 3, what is Neville Longbottom's greatest fear, revealed upon facing a boggart in Lupin's class?
Professor Snape.
<s>[INST] <<SYS>> Answer as briefly as you can to the following question. You are required to give a one-shot answer: <</SYS>> In Book 3, what is Neville Longbottom's greatest fear, revealed upon facing a boggart in Lupin's class? [/INST] Professor Snape. </s>