The chirality of RNA and DNA is primarily due to the D-sugar component of the nucleotides that make up the DNA and RNA strands. The sugar molecules in DNA and RNA, specifically deoxyribose and ribose, are in the D-configuration, which imparts chirality to the entire molecule. The chirality of the bases and the phosphate ester group is not the primary source of chirality in these molecules.
The correct answer is (A) : D-sugar component.