Find the odd number / letters / word from the given alternative.

The answer is A. Rectangle.

A rectangle is a four-sided polygon with four right angles. A square is a special type of rectangle with all four sides of equal length. A cube is a three-dimensional shape with six square faces. A triangle is a three-sided polygon.

Rectangles, squares, and cubes are all shapes that can be made up of squares. However, triangles cannot be made up of squares. Therefore, the odd number/letter/word from the given alternatives is A. Rectangle.