A Kennedy Class I modification 1 RPD requires:

Correct answer: B. Indirect retainers to prevent rotation around the fulcrum line

• A. Kennedy Class I is a distal extension case — indirect retainers are always needed.
• B. Correct. Kennedy Class I (bilateral distal extension) requires indirect retainers placed as far anterior from the fulcrum line as possible to resist rotation (lifting) of the distal extension bases away from the ridge under function. This is true for Class I regardless of modifications.
• C. Indirect retainers are needed on both sides for Class I (bilateral extension) — not just one side.
• D. Clasps alone without indirect retainers are insufficient for distal extension RPDs.

Note: The principle is that ALL Kennedy Class I (and Class II) distal extension cases require indirect retainers. The question on the INBDE typically targets Class I as the primary answer.