An area model shows regions with areas a², b², and two rectangular regions each of area ab. Which algebraic expression does this model represent?

Correct answer: a²+2ab+b²

The correct answer is B. The total area of a figure made from non-overlapping regions is found by adding the areas of all its parts. Here the parts have areas a², ab, ab and b². Therefore the total is a²+ab+ab+b² = a²+2ab+b². This is also the expansion of (a+b)², so the model represents the square of a+b. Option A subtracts the two ab regions, even though they are visible positive regions that must be added. Option C contains only a² and b² and omits both rectangular regions. Option D doubles the square regions and does not include the required ab parts. The coefficient 2 appears because there are two equal rectangles, not because either rectangle has area 2ab by itself. Memory cue: count every separate region and add its area; two ab regions produce +2ab.