Basically a mental and or physical break down.
Answer:With this system, blood always flows in only one direction inside the heart. There are also valves at the bottom of the large arteries that carry blood away from the heart: the aorta and the pulmonary artery. These valves keep the blood from flowing backward into the heart once it has been pumped out.
Explanation:
Because, when an infection exist in the human body it tends to spread, so if the cells stayed in one space then the infection would have a much greater opportunity to severly make that person very ill before the cells could even get to the infection.
Answer: Parasites
Explanation:
Both tapeworms and lice depend on a living host to survive. The relationship between the parasite, tapeworm or lice, isn't mutual. The parasite only benefits from the relationship, because the host provides them with plenty of nutrients. In some cases, tapeworms and lice can carry diseases and infect the host. So, there is your answer and goodluck!
