A quadrilateral having equal diagonals and equal opposite sides is always a ________.

Correct option is D

Given:
A quadrilateral has equal diagonals and equal opposite sides.
Concept Used:
Properties of special quadrilaterals:
In a rectangle: opposite sides are equal, and diagonals are equal.
In a rhombus: sides are equal but diagonals are not necessarily equal.
In a trapezium and kite: sides or angles may be equal but diagonals are generally not equal.
Solution:
For a rectangle:
Opposite sides are equal: AB = CD and AD = BC
Diagonals are equal: AC = BD

The given conditions match the properties of a rectangle.
So, the quadrilateral must be a rectangle.
Thus, the correct option is (d) Rectangle