Four different blood types are found in human populations because of and .

of your body's natural defences and presence or absence of certain antigens

Explanation:

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the answer is: metamorphic rocks often show the presence of fossils, also a

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imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.