## Core Concept
The question tests the understanding of molecular biology techniques, specifically blotting methods used for detecting different types of nucleic acids. RNA, DNA, and proteins are detected using specific blotting techniques.

## Why the Correct Answer is Right
Northern blotting is the technique used for detecting RNA molecules. It involves separating RNA samples according to size using electrophoresis, transferring them to a membrane, and then hybridizing them with labeled probes to detect specific RNA sequences. This method is crucial for studying gene expression at the RNA level.

## Why Each Wrong Option is Incorrect
* **Option A:** This option is incorrect because Southern blotting is used for detecting DNA, not RNA. It involves separating DNA fragments by size, transferring them to a membrane, and then using probes to detect specific DNA sequences.
* **Option B:** This option might seem plausible but is incorrect because there isn't a commonly recognized blotting technique by this letter associated with RNA detection in standard molecular biology texts.
* **Option D:** This option is incorrect because Western blotting is used for detecting proteins, not RNA. It involves separating proteins by size using electrophoresis, transferring them to a membrane, and then using antibodies to detect specific proteins.

## Clinical Pearl / High-Yield Fact
A key point to remember is the association of blotting techniques with the type of molecule being detected:
- **Southern blot** for DNA,
- **Northern blot** for RNA, and
- **Western blot** for proteins.
This association can help in quickly recalling the correct technique for RNA detection.

## Correct Answer: C. Northern blot.