Which area model has the whole square (a^2) and the inner remaining square ((a-b)^2)?

Correct answer: Square of difference model

Direct answer: B, the square-of-difference model. The outer square has side a, so its area is a². If strips of width b are removed from the appropriate sides, the side left for the inner square is a − b. Its area is therefore (a − b)². This is exactly the visual meaning of the identity (a − b)² = a² − 2ab + b². Option A is incorrect because the square-of-sum model uses a side a+b and produces (a+b)². Option C describes multiplying the dimensions of a rectangle, but it does not identify this special remaining-square arrangement. Option D concerns adding separate square areas and does not show an inner square obtained by subtraction. Memory cue: a reduced side a−b signals “difference,” while an enlarged side a+b signals “sum.”