Which feature most reliably differentiates RNA from DNA in most cells?

• A. RNA is found only in the nucleus, whereas DNA is found only in the cytoplasm.
• B. RNA is always double-stranded and uses thymine, whereas DNA is always single-stranded and uses uracil.
• C. RNA has a phosphate backbone but DNA does not.
• D. RNA typically contains ribose (with a 2′ $-OH$) and uracil, whereas DNA contains deoxyribose (2′ $-H$) and thymine.

Answer: (D)