The process of infection can be broken down into stages, each of which can be blocked by different defense mechanisms. In the first stage, a new host is exposed to infectious particles shed by an infected individual. The number, route, mode of transmission, and stability of an infectious agent outside the host determines its infectivity. Some pathogens, such as anthrax, are spread by spores that are highly resistant to heat and drying, while others, such as the human immunodeficiency virus (HIV), are spread only by the exchange of bodily fluids or tissues because they are unable to survive as infectious agents outside the body.
They are fat molecules that have no double bonds between carbon. Because they are saturated with hydrogen.
hope that helps.
Hmm. Let's see. I don't think it's D. And recognizing sources in stress does help, but I think the first thing is knowing that someone has too much stress, so i think the answer is A.
