## Core Concept
Cell ageing, also known as cellular senescence, refers to the process by which cells become older and exhibit changes in their behavior, structure, and function. This process is influenced by various factors, including telomere shortening, epigenetic changes, and accumulation of DNA damage.

## Why the Correct Answer is Right
The correct answer, , relates to the concept that cellular ageing is associated with **telomere shortening**. Telomeres are repetitive nucleotide sequences located at the ends of chromosomes, which protect them from deterioration or from fusion with neighboring chromosomes. Each time a cell divides, its telomeres naturally shorten due to the end-replication problem. When telomeres become critically short, cells can enter a state of senescence or undergo programmed cell death (apoptosis). This process acts as a tumor suppressor mechanism but also contributes to ageing.

## Why Each Wrong Option is Incorrect
* **Option A:** This option is incorrect because while **oxidative stress** and **DNA damage** do contribute to cellular ageing, they are not as directly and specifically associated with the ageing process as telomere shortening.
* **Option B:** This option is incorrect because **epigenetic changes** are indeed involved in ageing, but like oxidative stress, they are broader mechanisms and not as specifically pinpointed to the ageing process as telomere shortening.
* **Option D:** This option is incorrect because **accumulation of mutations** can contribute to ageing and age-related diseases, but it is not as directly linked to the cellular ageing process as telomere shortening.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **telomere length** can be used as a biomarker of ageing, and its shortening is associated with various age-related diseases. Understanding the role of telomeres in ageing has implications for potential therapeutic interventions aimed at delaying or reversing aspects of the ageing process.

## Correct Answer Line
**Correct Answer: C.**