Sodium reacts with water according to the reaction:

2Na(s)+2H2O(l)→2NaOH(aq)+H2(g)

Identify the oxidizing agent.

a) H2O(l)

b) NaOH(aq)

c) Na(s)

d) H2 (g)

a. H₂O. This is the oxidizing agent. It was reduced to oxidize the Na.

Explanation:

A redox reaction: 2Na(s)+2H₂O(l)→2NaOH(aq)+H₂(g)

Sodium changes from 0 (oxidation state) to +1. It has been oxidized.

It has released and electron.

H⁺ from water  has gained an electron, so it changed the oxidation state from +1 to 0. As the oxidation state has decreased, the element was reduced. So it won electrons.

In conclussion the water was reduced to hydrogen at ground state, to oxidized the Na. That's why H₂O is the oxidizing agent.