Reduction is the process by which eletrons are gained by an atom.
The answer is (4) amino acid. This molecule has one carboxyl and one amidogen linked at the same carbon atom. This is the property of amino acid. So this is an amino acid.
Ethanol is polar because the oxygen atoms attract electrons because of their higher electronegativity than other atoms in the molecule. Thus the -OH group in ethanol has a slight negative charge. Ammonia (NH3) is polar. Sulfur dioxide (SO2) is polar.
