Why does scrooge vow to change his ways in "stave iv: the last of the spirits"? a. the ghost of christmas future threatens to harm him if he does not change. b. he is inspired by the kind and gentle ways of the now-grown tiny tim. c. he recognizes the misery that will befall him and others if he does not change. d. he sees that the only way to save marley is to change his own behavior.