Answer to Question 1
Ans: D
The incubation period refers to the time of invasion to the time when disease symptoms first appear. A carrier is an individual who sheds pathogens without any disease symptoms. The period of replication before shedding of pathogens is called the latent period. The communicable period begins with the shedding of the pathogen agent.
Answer to Question 2
Ans: A
A chemical spill is an example of a man-made disaster. Droughts, earthquakes, and wildfires are examples of natural disasters.