Answer :
Final answer:
When a virus infects a person and the innate immune response is unable to eradicate the pathogen entirely from the body, adaptive immunity takes place, thus the correct answer is d) both a and b occur.
Explanation:
Adaptive immunity is triggered when the innate immune response fails to completely eliminate pathogens from the body, as indicated by option b. The innate immune system serves as the body's first line of defense against pathogens, utilizing nonspecific mechanisms such as inflammation and phagocytosis. However, in certain cases, the innate immune response may not be sufficient to completely clear the infection, allowing pathogens to persist within the body.
Moreover, adaptive immunity is also initiated when death results from pathogen infection, as mentioned in option a. In cases where the innate immune response is overwhelmed and unable to control the infection, the pathogen may proliferate rapidly, leading to severe illness and potentially death. In such circumstances, adaptive immunity is activated to provide a more targeted and specific defense against the invading pathogen.
Therefore, adaptive immunity occurs when both scenarios described in options a and b take place. It represents the body's secondary line of defense against pathogens, characterized by the activation of specific immune cells and the production of antibodies tailored to combat the particular pathogen.