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
Inosine is biological precursor of: 
Select and explain. 
A. Orotic acid and Uridylic acid, B. Uracil and Thymine, C. Adenylic acid, Guanylic acid, D. Purines and Thymine
C: Adenylic acid, Guanylic acid
Answer: C: Adenylic acid, Guanylic acid 
Explanation: IMP (Inosine Mono Phosphate) the first purine nucleotide to be formed. It is the parent nucleotide which synthesize AMP & GMP and then diphosphate and triphosphate forms can be synthesized.