Final answer:
DNA lacks the 2' hydroxyl group because its sugar is deoxyribose, resulting in increased resistance to degradation and greater stability compared to RNA.
Step-by-step explanation:
DNA lacks the 2' hydroxyl group because its sugar is deoxyribose, which has a hydrogen atom attached to the 2' carbon. This difference in sugar composition between DNA and RNA is one of the primary reasons why DNA is more stable than RNA. The absence of the 2' hydroxyl group also makes DNA more resistant to degradation compared to RNA, which has the hydroxyl group. Therefore, option D. Increased resistance to degradation is the correct reason why the 2' hydroxyl group is lacking in DNA.