Arrange the following preparations in increasing order of their resisting area: (A) A < B < C, (B) B < A < C, (C) C < B < A, (D) C < A < B
Answer is C. The resisting area decreases as the preparation taper increases.

For a cylinder with no taper, the resisting area would cover half the axial walls (A).
For an deafly-tapered tooth preparation, the resisting area covers somewhat less than half the axial walls (B).
An over-tapered (20 degrees) preparation has only a small resisting area near the occlusal surface (C).