Nitrous oxide

Air pollutant photochemical oxidants include (a) nitrous oxide, nitric acid and nitric oxide (b) oxygen, chlorine and nitric acid (c) ozone, peroxyacetyl nitrate and aldehydes (d) carbon monoxide and sulphur dioxide

Nitrous acid acts as oxidant as well as reductant. Give suitable examples.

Nitrous acid behave as an oxidant as well as a reductant - why ?