Which of the following elements is the odd one?

Sulphur, bromine and helium cannot conduct electricity because they are made up of molecules. Non-metals normally adopt simple molecular structures.
However, carbon (in the form of graphite) conducts electricity.
Carbon (in the form of graphite) is also a non-metal but it adopts a giant covalent structure. Each carbon atom is covalently bonded to three other carbon atoms. The fourth outermost electron remains unbonded and is delocalized throughout the structure. These delocalized electrons are responsible to conduct electricity.