(d) : $DNA$ or deoxyribose nucleic acid is the largest macromolecule made of the helically twisted two antiparallel polydeoxyribonucleotide strands held together by hydrogen bonds. The two strands of $DNA$ are together called $DNA$ duplex. It has a diameter of $20\ \mathring A $. One turn spiral has a distance of $34\ \mathring A $. It contains $10$ deoxyribonucleotides in each strand so that the distance between two adjacent nucleotides is $3.4\ \mathring A $.