Fat and oil-containing food items are flushed with nitrogen, why?

Identify the substances that are oxidized and the substances that are reduced in the following reaction;

$4\mathrm{Na}\left(\mathrm{s}\right) +{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{Na}}_2\mathrm{O}\left(\mathrm{s}\right)$

Identify the substances that are oxidized and the substances that are reduced in the following reaction:

$\mathrm{CuO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)\to \mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Which of the statements about the reaction given below are not correct?

$\mathrm{PbO}\left(\mathrm{s}\right)+\mathrm{C}\left(\mathrm{s}\right)\to 2\mathrm{Pb}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$

(a) Lead is reduced.

(b) Carbon dioxide is oxidised.

(c) carbon is oxidised.

(d) Lead oxide is reduced.