Match List - I with List - II and choose the correct answer.

List - I	List - II
(a) Protein	(i) C = C double bonds
(b) Unsaturated fatty acid	(ii) Phosphodiester bonds
(c) Nucleic acid	(iii) Glycosidic bonds
(d) Polysaccharide	(iv) Peptide bonds

To match List - I with List - II, we analyze the characteristic chemical bonds or features associated with each biological molecule:

(a) Protein: Proteins are polymers of amino acids. The amino acids are linked together by peptide bonds (iv), which are covalent amide bonds formed between the carboxyl group of one amino acid and the amino group of another.

(b) Unsaturated fatty acid: Unsaturated fatty acids contain one or more C = C double bonds (i) in their hydrocarbon chains, unlike saturated fatty acids which have only single carbon-carbon bonds.

(c) Nucleic acid: Nucleic acids (DNA and RNA) are polymers of nucleotides. The nucleotides in a strand are joined together by phosphodiester bonds (ii), which link the 3' carbon of one sugar molecule to the 5' carbon of another.

(d) Polysaccharide: Polysaccharides are carbohydrates composed of monosaccharide units. These sugar units are linked together by glycosidic bonds (iii), which are covalent bonds formed between a hemiacetal or hemiketal group of a saccharide and the hydroxyl group of another compound.

Matching these definitions, we get:
(a) matches with (iv)
(b) matches with (i)
(c) matches with (ii)
(d) matches with (iii)

Therefore, the correct matching option is a - (iv) b - (i) c - (ii) d - (iii).