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Basically because your skin has several layers to it (see link, below), and the layer that has the blood vessels capable of bleeding in it is further down than a superficial scrape would affect.
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I answer i would choose is C
Here, you go:
Answer:
<u><em>Generation of B Cells. The immune system is remarkable for its ability to respond to a great many antigens.</em></u>
Explanation:
<u><em>These cells make antibodies which defends and fights out viruses in our bodies.</em></u>
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<em>~Hope This Helps~</em>
