Final answer:
The series of components that lead to infection are referred to as the Chain of infection. This chain includes several stages, such as exposure, adhesion, invasion, infection, and transmission. Option a is correct.
Step-by-step explanation:
The series of components that lead to infection are referred to as the Chain of infection. This chain includes several stages, such as exposure, adhesion, invasion, infection, and transmission. Pathogens enter the body through portals of entry and leave through portals of exit.
The pathogen must be able to gain entry to the host, travel to the location where it can establish an infection, evade or overcome the host's immune response, and cause damage to the host.