If the layout for a rectangular building is square, what can be said about its diagonals?

In a square, which is a specific type of rectangle, all four sides are equal in length, and each internal angle is a right angle. One of the fundamental properties of squares is that the diagonals connect opposite corners and bisect each other at right angles. Moreover, the diagonals of a square are congruent, meaning they are of equal length.

When a rectangular building has a square layout, it inherently means that all sides are equal. This leads to a situation where both diagonals must also be equal because they are the same line segment extending from one corner of the square to the opposite corner. Therefore, the correct statement is that the diagonals are equal, reflecting an essential property of squares.

In contrast, with the other options, while it's true that diagonals can form different relationships in various shapes, in a square, the diagonal's length is not twice that of the sides, nor do they form a right angle in the way described in the other choices. Understanding these properties helps affirm the significance of the square's geometry.