I believe your answer would have to be A. " he"
This quote is trying to explain how powerful the human brain thoughts can be , it can control you and eat you alive if you over think. sort of like if you think your sick by you over thinking it it’s scienctifically proven you can make yourself sick by over thinking , hope this helps
Bob Ewell attacks them because it's his revenge for Atticus defending Tom and showing Bob how to be a liar. Boo Radley saves them