The human immunodeficiency virus (HIV) that causes the disease known as aids selectively infects helper T cells (CD4+).
This retrovirus also infects macrophages and dendritic cells. When CD4+ T cell numbers decrease below a critical level (due to the killing of this cells with different mechanisms), cell-mediated immunity is lost. As a result, the body becomes progressively more susceptible to infections, leading to the development of AIDS.
<span> HIV can be transmitted only via body fluids like blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, and breast milk, which means that people usually get or transmit HIV through sexual behaviours and use of the needle. For HIV infection, these fluids must come in direct contact with a mucous membrane or damaged tissue. Another way is to be directly injected into the bloodstream (from a needle for example).</span>
Answer:
D. They float on convection currents in the mantle.
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Answer:
Stretching is a sign of growing, also known as having a growth spurt. Your body stretches in order to make room for things growing, for example, how a pregnant woman's stomach stretches to make room for her unborn baby.
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Answer: The taproot
Explanation: A deep taproot helps plants use moisture held in deeper soil layers, and they can have great drought resistance compared to fibrous-rooted plants. An example is honey mesquite (Prosopis juliflora), which is known to send its roots down 150 feet to get water.
