Soluble RNA is

Options

A. tRNA
B. mRNA
C. rRNA
D. hnRNA

Answer

### Step-by-Step Solution:

1. **Understanding Soluble RNA**: The question asks about soluble RNA, which refers to a type of RNA that can dissolve in a salt solution.

2. **Identifying Types of RNA**: The options provided are tRNA (transfer RNA), mRNA (messenger RNA), rRNA (ribosomal RNA), and hnRNA (heterogeneous nuclear RNA). We need to determine which of these is classified as soluble RNA.

3. **Defining tRNA**: Transfer RNA (tRNA) is a type of soluble RNA. It is known as an adapter molecule because it helps translate the genetic code into proteins.

4. **Characteristics of tRNA**: tRNA typically consists of 76 to 90 nucleotides in length. It plays a crucial role in protein synthesis by linking the nucleotide sequence of mRNA to the corresponding amino acids.

5. **Physical Link**: tRNA serves as a physical link between the nucleotide sequence (from mRNA) and the amino acid sequence (in proteins). This function is essential for the translation process in protein synthesis.

6. **Solubility in NaCl**: tRNA is soluble in 1 molar NaCl, which is why it is referred to as soluble RNA.

7. **Conclusion**: Based on the characteristics and functions described, the correct answer to the question "Soluble RNA is" is tRNA.

### Final Answer:
**Soluble RNA is tRNA.**

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