**Core Concept**
Telomeres are repetitive nucleotide sequences located at the ends of eukaryotic chromosomes, protecting them from deterioration or fusion with neighboring chromosomes. **Telomerase** is an enzyme that extends telomeres by adding nucleotides to the existing telomere sequences. This process is crucial for maintaining chromosome integrity and stability.

**Why the Correct Answer is Right**
The correct answer is related to the function and implications of telomerase and telomeres. **Telomerase** activity is indeed increased in cancer cells, which allows them to divide indefinitely by preventing telomere shortening. This is a key factor in cancer cell immortality. **Telomerase** is a type of **reverse transcriptase**, which is an **RNA-dependent DNA polymerase**, not a DNA-dependent RNA polymerase.

**Why Each Wrong Option is Incorrect**
**Option C:** DNA-dependent RNA polymerase is incorrect because telomerase is actually an RNA-dependent DNA polymerase.
**Option D:** DNA polymerase is incorrect because, while it is involved in DNA replication, telomerase is a specific type of reverse transcriptase.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that increased **telomerase** activity is a hallmark of cancer cells, allowing them to achieve immortality by maintaining their telomeres.

**Correct Answer:** B. Increased telomerase activity favours cancer cells