A parallelogram having all sides equal and diagonals unequal is called a:

Correct option is B

Solution:

Rhombus:

A rhombus is a type of parallelogram where all four sides are of equal length.

The diagonals of a rhombus are unequal and they bisect each other at right angles (90 degrees).

Square:

A square has all four sides of equal length, and the diagonals are also equal in length. It is a special type of rhombus where the angles are all right angles.

Kite:

Two pairs of equal adjacent sides, diagonals intersect at right angles but are not equal.

​Rectangle:

A rectangle is a parallelogram with opposite sides equal and all angles being right angles. The diagonals of a rectangle are equal in length. 

Thus,  The correct answer is (b) rhombus

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