Answer: zinc is the reducing agent.
Explanation:
1) Reducing agent is the agent that releases electrons, is oxidized (its oxidation number increases) and causes the reduction of the other agent (the reduced spices reduces its oxidation state).
2) Chemical equation:
Zn(s) + HCl (aq) → H2(g) + ZnCl2(s)
3) determine the oxidation states of each spices
Zn (s): oxidation state = 0
Zn in ZnCls: oxidation state = + 2.
Therfore Zn was oxidized and is the reducing agen.
H in HCl: oxidtation state = +1
H in H2: oxidation state = 0
Therefore H2 was reduced (it is the oxidizing agent).