Which is the correct classification of the area parts in the square visual model of (a+b)²?

Correct answer: One a² square, two ab rectangles, and one b² square

The correct answer is A. Imagine a large square whose side is a+b. Divide each side into parts of lengths a and b. The four resulting regions are an a-by-a square with area a², an a-by-b rectangle with area ab, a b-by-a rectangle with area ab, and a b-by-b square with area b². Adding them gives a² + ab + ab + b² = a² + 2ab + b², which is the identity (a+b)². Option B misses one of the two mixed rectangles, so it gives only ab instead of 2ab. Option C uses the wrong number and types of squares. Option D ignores the two square regions and incorrectly treats every region as an ab rectangle. Memory cue: the two cross-shaped regions are responsible for the coefficient 2 in 2ab.