**Core Concept:** Cell ageing refers to the natural decline in cellular function and regenerative capacity that occurs over time, leading to increased susceptibility to diseases and reduced tissue repair. In humans, this process is influenced by genetic, epigenetic, and environmental factors.

**Why the Correct Answer is Right:** The correct answer (C) is referring to the concept of senescence, which is a natural part of cellular ageing. Senescence is a permanent cell cycle arrest characterized by a secretory phenotype (SASP), increased oxidative stress, and genomic instability. This process contributes to tissue homeostasis, but excessive senescent cells can impair tissue function and promote age-related diseases.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because it refers to apoptosis, which is a programmed cell death process involved in tissue homeostasis and development. Apoptosis is distinct from senescence and is not a true aspect of cell ageing.

B. This option is incorrect because autophagy is a cellular process involved in degradation and recycling of cellular components, essential for maintaining cellular homeostasis. While autophagy can contribute to cellular longevity, it is not directly related to cell ageing as described in the question.

D. This option is incorrect because necrosis is an uncontrolled cell death process resulting from tissue injury or infection, not a component of cell ageing.

**Clinical Pearl / High-Yield Fact:** Understanding cell ageing and its mechanisms (senescence, apoptosis, autophagy, and necrosis) is essential for understanding tissue homeostasis, age-related diseases, and the development of regenerative medicine strategies.

**Correct Answer:** C. Senescence is a key aspect of cell ageing, contributing to tissue homeostasis and age-related diseases.