Based on the CDC guidelines a person with a CD4+ cell count between 200-400 is regarded as being in <u>the second stage</u> of the HIV infection.
Acquired Immunodeficiency Syndrome
Acquired immunodeficiency syndrome (AIDS) is a condition caused by HIV (human immunodeficiency virus). AIDS is a chronic disorder and can become life-threatening for the infected person. The HIV viruses reproduce inside the host and while doing so they destroy the CD4+ immune cells which reduce the person's ability to fight against other diseases.
CD4+ cell count and AIDS
According to the CDC (U.S. Centers for Disease Control and Prevention), HIV infection is categorized into different stages based on the number of CD4+ cells.
- Stage 1: - CD4+ cell count is more than 500 per microlitre. There are no symptoms or AIDS-related conditions.
- Stage 2: - CD4+ cell count is more than 500 per microlitre. There are no symptoms or AIDS-related conditions.
- Stage 3: - The CD4+ cell count falls below 200 and AIDS-related symptoms and conditions are present.
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Answer:
The correct answer is option - C. They replaced carbon dioxide with oxygen in the atmosphere.
Explanation:
Cyanobacteria or Blue-green algae is a group of bacteria that is making its own food using water and carbon dioxide in the presence of sunlight, the process of photosynthesis
These organisms release oxygen as a byproduct of photosynthesis in the atmosphere. Through this process, these organisms replaced carbon dioxide with oxygen in the atmosphere in the early earth.
Thus, the correct answer is option C. They replaced carbon dioxide with oxygen in the atmosphere.
