**Core Concept**
Senescent cells are characterized by a state of permanent cell cycle arrest, often resulting from DNA damage or telomere shortening. This cellular senescence is associated with various age-related diseases and is influenced by the activity of specific cellular pathways.

**Why the Correct Answer is Right**
Senescent cells exhibit reduced or absent telomerase activity, leading to progressive telomere shortening. Telomerase is a reverse transcriptase that extends telomeres by adding nucleotides to the 3' end of telomeres. The lack of telomerase activity in senescent cells prevents telomere elongation, contributing to cellular aging. This is in contrast to stem cells and cancer cells, which often exhibit high telomerase activity.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** While senescent cells do exhibit changes in protein expression and epigenetic modifications, this is not the primary characteristic that defines them.
* **Option C:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
It is essential to note that cellular senescence is a distinct process from apoptosis (programmed cell death) and is characterized by the presence of senescence-associated beta-galactosidase (SA-β-Gal) activity.

**Correct Answer:** Not enough information to provide a correct answer.