Answer :
Final answer:
ALL OF THE ABOVE, An infectious disease can only be passed from one person to another when a pathogen is present, it has a way to enter the body, and there are enough of the pathogen to cause an infection.
Explanation:
In order for an infectious disease to be passed from one person to another, several factors must be in place. Firstly, a pathogen, which is a bacterium, virus, or other microorganism that can cause disease, needs to be present. Secondly, this pathogen has to enter a host through an entry site. This could be through breaks in the skin, inhalation, ingestion, or through the mucous membranes. Thirdly, for a person to actually get sick, enough of the pathogen needs to be present. This is known as the infectious dose. It is the number of pathogen cells or viruses needed to establish an infection. So, the correct answer to your question is ALL OF THE ABOVE.
Learn more about Infectious Disease
https://brainly.in/question/49350933
#SPJ1