Observe the given picture and identify (A) and (B) ?

(A) Base pairs (B) Sugar phosphate backbone.

The correct answer is Option (2)- (A) Base pairs (B) Sugar phosphate backbone .

               DNA double helix

The chemical structure of a polynucleotide chain (DNA or RNA):  A nucleotide has three components – a nitrogenous base, a pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and a phosphate group. There are two types of nitrogenous bases – Purines (Adenine and Guanine), and Pyrimidines (Cytosine, Uracil and Thymine). Cytosine is common for both DNA and RNA and Thymine is present in DNA. Uracil is present in RNA at the place of Thymine.