I believe c is the correct answer.
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.
Answer: During sexual intercouarse a males ejaculation fertilizes the egg and is released. Once the egg travles to the uterus. It will usually implant in endometrium. From there a hormone called human chorionic gonadotropin begins to produce in the uturus. This is the hormone that a pregnancy test measures. It prevents the uterine lining from being shed, so the woman does not have a period. Resulting in pregnancy.
1. Cardiovascular System
2. Muscular System
