An element 'E' exists in three allotropic forms 'A', B and C, In allotrope 'A' the atoms of element 'E' are joined to form spherical molecules. In allotrope 'B' each atom of element 'E' atoms to form a sheet like structure. In allotrope 'C' each atom of elements 'E' is surrounded by four other 'E' atoms to form a rigid structure. Then name which allotrope is used in making anode of a dry cell ?