Question

the individual at risk for developing an infection from the disease is called the
host
reservoir
mode of transmission
portal of entry

Explanation:

In the context of disease transmission, the host is the individual who is at risk of developing an infection. A reservoir is a source where the pathogen lives (e.g., a person, animal, or environment). Mode of transmission refers to how the pathogen spreads (e.g., direct contact, airborne). Portal of entry is the way the pathogen enters the host (e.g., respiratory tract, broken skin).

Answer:

Host