This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basics of genetics, Subject name: Biochemistry
The commonest form of DNA variation is: 
Select and explain. 
A. Single nucleotide polymorphism, B. Copy Number Variations (CNVs), C. Transposons, D. Mutations
A: Single nucleotide polymorphism
Answer: A: Single nucleotide polymorphism 
Explanation: SNPs most common polymorphisms. There are 3 million SNPs in the human genome. A single nucleotide at a paicular location is variable