This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nucleotides, Subject name: Biochemistry
Most abundant free nucleotide in a mammalian cell ? 
Select and explain. 
A. ATP, B. dATP, C. GTP, D. AMP
A: ATP
Answer: A: ATP 
Explanation: Most abundant free nucleotide in a mammalian cell is ATP