Genome represents the total amount of DNA present in the haploid set of chromosomes. The haploid amount of DNA is also referred to as C-value which is 2.8 picograms or 2.75 X 109 basepairs. Since, DNA is a double stranded molecule, the size of genome is given in base pairs which also shows the total number of nucleotides in the genome. Thus, total number of nitrogenous bases in human genome is estimated to be about 3.1 billion. Correct option is "D".