Final answer:
Stress-Induced Programmed Cell Death (PCD), specifically apoptosis, can be activated by pathogen invasion, which prompts a cell to initiate a controlled death process to eliminate the threat posed by the pathogen (option A).
Step-by-step explanation:
Stress-Induced Programmed Cell Death (PCD), a critical process that ensures cellular homeostasis, is activated by a variety of stressors. Among the options provided, A. Pathogen invasion is a recognized trigger for the activation of programmed cell death. This mechanism allows a cell to die in a controlled way, which is important to prevent the release of potentially harmful molecules from inside the cell and to maintain the health of the overall organism.
Apoptosis, a form of PCD, can be induced by external factors such as pathogen invasion when PAMPs (pathogen-associated molecular patterns) are recognized by a cell. This recognition leads to a cascade of events resulting in apoptosis in order to eliminate the threat posed by the pathogen.
HEnce, the answer is option A.