Which among the following group 16 elements exists in more than two allotropic states? (JCECE 2014)

Element Allotropes (a) Polonium α- and β-polonium (b) Tellurium None (c) Selenium Trigonal, rhombohedral, three deep red monoclinic forms (α, β and γ-amorphous red, black vitreous selenium). (d) Oxygen Dioxygen and ozone