Answer:
Option (B)
Explanation:
Coordinates of the vertices of the rectangle were A(0, 0), B(a, 0), C(a, b) and D(0, b)
Formula to determine the distance between two points with the vertices (x, y) and (x', y') is,
d =
For the length of AD,
AD =
=
= b
Therefore, Option (B) will be the answer.