Concept:The electrochemical series arranges elements by their standard electrode potentials; strongly reducing metals are placed at the top.
Explanation:Elements at the top lose electrons easily and are the strongest reducing agents.
Sodium is an active alkali metal with a high tendency to form
Na+ ions.
Its standard electrode potential is negative, so it appears above hydrogen in the series.
Copper is less reactive than sodium and hydrogen, while oxygen is an oxidising agent that gains electrons.
Thus, among the listed options, sodium is the most electropositive element.
Answer:Sodium (Option C).