RNA differs from DNA in that:

• A. RNA contains the sugar ribose, while DNA contains deoxyribose.
• B. RNA is found only in the nucleus, while DNA is found throughout the cell.
• C. RNA uses the base thymine, while DNA uses uracil.
• D. RNA is always double-stranded, while DNA is always single-stranded.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the structural differences between RNA and DNA, focusing on the sugar component in their nucleotides. RNA contains ribose sugar, whereas DNA contains deoxyribose sugar, which lacks one oxygen atom compared to ribose.
2. Step 2: Examine the location of RNA and DNA within the cell. RNA is not restricted to the nucleus; it can be found both in the nucleus and the cytoplasm, while DNA is primarily located in the nucleus (and mitochondria).
3. Step 3: Compare the nitrogenous bases used in RNA and DNA. RNA uses uracil (U) instead of thymine (T), which is found in DNA. This is a key difference in their base composition.
4. Step 4: Analyze the strand structure of RNA and DNA molecules. DNA is typically double-stranded forming a double helix, whereas RNA is usually single-stranded.
5. Step 5: Summarize the correct differences: RNA contains ribose sugar, uses uracil instead of thymine, is usually single-stranded, and is found in both nucleus and cytoplasm; DNA contains deoxyribose sugar, uses thymine, is double-stranded, and is mainly in the nucleus.