**Core Concept**
DNA nick and labelling (in situ) technique is a molecular biology method used to detect and study DNA replication, repair, and recombination events in living cells. This technique involves introducing a label into the DNA strands at specific sites, allowing researchers to visualize and analyze the labelled DNA.

**Why the Correct Answer is Right**
The DNA nick and labelling technique involves making a single-strand break (nick) in the DNA, followed by the incorporation of a labelled nucleotide into the nick. This labelled nucleotide serves as a marker for DNA replication, repair, or recombination events. The technique can be used to study the kinetics of DNA replication, identify specific DNA sequences involved in replication, and analyze the effects of various factors on DNA replication.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because DNA nick and labelling is not primarily used to study DNA transcription.
**Option B:** This option is incorrect because DNA nick and labelling does not involve the use of radioactive labels, but rather fluorescent or other types of labels.
**Option C:** This option is incorrect because DNA nick and labelling is not a technique used to study protein synthesis.

**Clinical Pearl / High-Yield Fact**
A key application of the DNA nick and labelling technique is in the study of cancer biology, where it can be used to analyze the kinetics of DNA replication and identify specific DNA sequences involved in tumour formation.

**Correct Answer: B. DNA replication and repair events.**