Select the option in which the words share the same relationship as that shared by the given pair of words.
Square: Pentagon :: ?

Square and Pentagon are two dimensional closed loop geometry shapes.

Square has 4 sides and Pentagon has 5 sides, so side difference is 1.

Similarly,

Triangle and Rhombus are two dimensional closed loop geometry shapes.

Triangle has 3 sides and Rhombus has 4 sides, so side difference is 1.

Radius: Perimeter – Radius is the distance from the center to the boundary of a circle, while the perimeter (circumference) is the total boundary length.

Side: Angle – A side is a straight edge of a polygon, and angles are formed between two intersecting sides.

Diagonal: Hypotenuse – A diagonal is a line joining two opposite vertices of a polygon, while the hypotenuse is the longest side of a right triangle.

Thus, correct option is (b).