A sketch that does not show a right triangle that can be used to find the length of the diagonal is: D. diagram D.
In Mathematics and Euclidean Geometry, a rectangle refers to a type of quadrilateral or polygon in which its opposite sides are equal and all the angles that are formed are right angles, measuring 90 degrees.
Generally speaking, the diagonals of a rectangle divide it into two equal parts and this ultimately implies that, the two diagonals of any rectangle are congruent.
By critically observing the sketches shown above, we can logically deduce that only diagram D has a triangle that cannot be used to find the length of the diagonal because it does not represent a right-angled triangle.