12 CFR §269b.121

1. (a)A specific admission or denial, and where appropriate, explanation thereof; or if the respondent is without knowledge of the allegation, he shall so state and such statement shall operate as a denial. Admissions or denials may be to all or part of an allegation but shall be responsive to the substance of the allegation;
2. (b)A specified, detailed statement of any affirmative defense;
3. (c)A clear and concise statement of the facts and matters of law relied upon constituting the grounds of defense.