Which of the following is not an allotropic form of sulphur?

Roll sulphur

The correct answer is option 1. Roll sulphur.

Allotropes are defined as chemical elements which exist in two or more different forms, in the same physical state or allotropes are defined as different structural modifications of an element, the atoms of the element are bonded together in a different manner. At present, about 30 well-characterized sulphur allotropes are known. Commonly known allotropes of sulphur are:

Rhombic sulphur

Monoclinic sulphur

Plastic sulphur ( also known as gamma-sulphur)

Roll sulphur is not the allotropic form of sulphur.