B. As a resource for locating credible sources for him to consult.
Answer:
Spitz was always looking for a way to attack Buck it is probably necessary that Buck kill him. If he hadn't killed him, it is likely that Spitz would have killed Buck.
Explanation:
they want to leave a note to Boo, who Jem considers to be his friend. However, when they get to the tree, Mr Radley is seen to be filling the tree with cement, a very deliberate way of stopping Boo and the children's communication. This suggests he is a mean and strict man.
