This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Human genome contains --- base pairs 
Select and explain. 
A. (3 x 10 )9, B. (3 x 10 )8, C. (3 x 10 )7, D. (3 x 10 )6
A: (3 x 10 )9
Answer: A: (3 x 10 )9 
Explanation: The haploid human genome (containing only 1 copy of each chromosome) consists of roughly 3 billion of these base pairs grouped into 23 chromosomes. A human being inherits two sets of genomes (one from each parent), and thus two sets of chromosomes, for a total of 46 chromosomes, representing the diploid genome, which contains about 6x10^9 base pairs.