>Here is the task is to determine the communal reaction to crime. The writer maintains that the criminal justice system of punishments allows the community to purge itself of its anger, its sense of outrage at the criminal's acts. Thus, it provides a catharsis or purgation for the community.
Remember in double blank sentences, go through the answers, testing the first word in each choice and eliminating those that do not fit. In this case you can readily eliminate.
Choices B and D: it is unlikely that an essential purpose of the criminal justice system would be the provision of either a disclaimer (denial or disavowal, as in disavowing responsibility for a legal claim) or a document.