Final answer:
Pathogens rely on a host for nutrition and growth, and the correct term for such an organism is a host, not a vector, reservoir, or carrier.
Step-by-step explanation:
Many pathogens require a host to provide nutrition and a place to multiply. This can be an animal, insect, or human whose body is capable of sustaining the growth of a pathogen. The correct answer is a) Host. For example, mosquitoes serve as hosts for the West Nile virus, whereas ticks can carry the bacteria that cause Lyme disease. Both organisms are examples of vectors that transfer pathogens between hosts, but the host is the specific term for the organism that supports the pathogen's survival directly by providing nutrition and an environment for multiplication.