**Core Concept**
Northern blotting is a molecular biology technique used to detect specific RNA sequences in a sample by hybridizing labeled probes to RNA molecules separated by size via gel electrophoresis.

**Why the Correct Answer is Right**
Northern blotting specifically detects RNA transcripts. RNA samples are separated by size on a denaturing gel (usually agarose), transferred to a membrane, and then hybridized with a labeled DNA or RNA probe. The probe binds only to complementary RNA sequences, allowing detection of gene expression levels and RNA size. This technique is distinct from Southern blot (DNA) and Western blot (proteins).

**Why Each Wrong Option is Incorrect**
Option A: Western blot detects proteins using antibodies, not RNA, so it is not applicable.
Option C: Southern blot is used for DNA analysis, not RNA, and involves DNA hybridization.
Option D: Northern blot is the correct technique for RNA, so "none" is incorrect.

**Clinical Pearl / High-Yield Fact**
Remember the acronym **"N" for Northern blot – it stands for RNA**. This helps distinguish it from Southern (DNA) and Western (protein) blots. Always associate Northern blot with gene expression studies.

✓ Correct Answer: B. Northern blot