**Core Concept**
The underlying principle being tested is the process of DNA replication, specifically focusing on the replication of chromosome ends. This involves **telomere** replication, which is crucial for maintaining chromosome integrity.

**Why the Correct Answer is Right**
The correct answer involves the mechanism by which **telomeres**, the protective caps at the ends of chromosomes, are replicated. This process is mediated by an enzyme called **telomerase**, which is a reverse transcriptase that adds nucleotides to the ends of chromosomes, thereby maintaining their length.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the mechanism of telomere replication.
**Option B:** Similarly, this option is incorrect as it does not involve the enzyme responsible for telomere replication.
**Option D:** This option is also incorrect as it is unrelated to the process of telomere replication.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **telomerase** plays a critical role in cancer cells, allowing them to divide indefinitely by maintaining their telomeres.

**Correct Answer:** D. Telomerase