**Core Concept**
mRNA (messenger RNA) is a single-stranded RNA molecule that plays a crucial role in protein synthesis by carrying genetic information from DNA to the ribosome. The codons present on mRNA are sequences of three nucleotides that specify particular amino acids during translation.

**Why the Correct Answer is Right**
mRNA is synthesized in the nucleus through the process of transcription and is then transported to the cytoplasm, where it serves as a template for protein synthesis. The sequence of nucleotides on mRNA determines the sequence of amino acids in a protein, as each codon on the mRNA molecule corresponds to a specific amino acid. This is achieved through the interaction of the ribosome with the codons on the mRNA molecule, allowing for the assembly of amino acids into a protein. The codons on mRNA are read in a sequence of three nucleotides at a time, known as a codon, and each codon specifies one of the 20 amino acids that make up proteins.

**Why Each Wrong Option is Incorrect**
**Option A:** tRNA (transfer RNA) molecules do not contain codons for specific amino acids; instead, they are responsible for transferring amino acids to the ribosome during protein synthesis, with each tRNA molecule recognizing a specific codon on the mRNA molecule.
**Option B:** rRNA (ribosomal RNA) is a component of the ribosome, where protein synthesis takes place, but it does not contain codons for specific amino acids.
**Option D:** The statement "None" is incorrect, as mRNA is indeed the type of RNA that contains codons for specific amino acids.

**Clinical Pearl / High-Yield Fact**
A key characteristic of mRNA is that it is single-stranded, whereas DNA is double-stranded. This single-stranded nature of mRNA makes it more susceptible to degradation by enzymes, which can affect protein synthesis.

✓ Correct Answer: C. mRNA