Answer: Magnesium Mg
Step-by-step explanation:
Oxidization is the process by which a substance either gains oxygen or losses electrons.
The chemical reaction of the above is denoted by,
Mg(s) + 2HCl(aq) -----> MgCl2(aq) + H2(g)
Mg went from a 0 to a +2 state which would mean that it lost electrons.
It was therefore oxidized.
Please do react or comment if you need clarification or if the answer helped you. This can help other users as well. Thank you.