AIDS is the most severe phase of HIV infection, when a person’s immune system is severely weakened. When HIV weakens the immune system opportunistic infections occur in the body. The low number of helper T cells in the blood and the badly damaged immune systems leads the infected to get an increasing number of severe illnesses, called opportunistic illnesses. Opportunistic infections are infections caused by pathogens that take advantage of an opportunity not normally available.
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Bone marrow is the answer,pls check If I am correct
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.
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