Final answer:
DNA's chemical stability is primarily due to the presence of deoxyribose sugar, which makes it less reactive and less prone to hydrolysis, as opposed to the ribose sugar in RNA.
Step-by-step explanation:
The chemical stability of DNA is often attributed to its structural features, which differ from those of RNA. One of the key reasons that DNA is chemically more stable than RNA is the presence of deoxyribose sugar in its nucleotides, as opposed to ribose sugar found in RNA.
The absence of the hydroxyl group (-OH) at the 2' position in the deoxyribose sugar of DNA makes it less reactive and less susceptible to hydrolysis. Furthermore, DNA's double-helical structure provides physical stability and protection to the genetic code. Thymine, rather than uracil, contributes to this stability because thymine forms more stable hydrogen bonds with adenine than does uracil. But it is not thymine itself that fundamentally increases DNA's chemical stability.
Similarly, the presence of adenine and guanine does not directly confer stability, as these nitrogenous bases are also found in RNA. Thus, the most direct attribute of DNA that contributes to its chemical stability, among the options listed, is the presence of deoxyribose sugar, which is less prone to chemical degradation.
In summary, the correct option answer that explains the chemical stability of DNA is the presence of deoxyribose sugar (option 3).