Answer:
The correct answer to this is Mg.
Explanation:
Mg is the second element at the Periodic Table, down Be. As its the oxidation number is 2, it can release two electrons to form compounds. Not like C that is tetravalent, or Na that is a monovalent element (1e-). Si, as C has 4 oxidation states, and phosphorus can lose or get 3 e- (for example PCl3), also get 5e- (for example P2O5)
