Which type of nucleic acid is characterized by being single-stranded and containing ribose?

The correct answer is RNA. This type of nucleic acid is defined by its structure, which consists of a single strand of nucleotides. Each nucleotide in RNA contains a ribose sugar, whereas DNA has a deoxyribose sugar. The presence of ribose in RNA is a key distinguishing feature that contributes to its functionality in biological systems, such as its role in protein synthesis and various regulatory functions.

While mRNA and tRNA are specific types of RNA, the general term "RNA" encompasses all forms, including these. Therefore, the broad categorization of RNA captures the essential characteristics of being single-stranded and containing ribose. Understanding RNA's role in the synthesis of proteins and its various types helps clarify why the answer is correct.