How does RNA differ from DNA?

RNA differs from DNA primarily in its structure and composition. The correct answer highlights two key features of RNA: it contains ribose sugar and is typically single-stranded.

Ribose sugar, which has one more oxygen atom than the deoxyribose sugar found in DNA, is a central component of RNA. This difference in sugar types contributes to the overall structural differences between the two nucleic acids. Additionally, RNA is generally found as a single strand, while DNA is famously double-stranded, forming a helical structure.

These attributes of RNA play crucial roles in various biological functions, such as protein synthesis and regulation of gene expression, which diverges significantly from DNA's role in long-term genetic storage and transmission.

The other options do not accurately represent the characteristics of RNA. For instance, RNA is not double-stranded nor does it contain thymine; instead, it contains uracil. Furthermore, RNA does have a sugar backbone, and it is composed of nucleotides rather than being made entirely of proteins.