[Q]: What is the missing first step of the following process: - Nephrons in the kidney filter the blood - The waste that is filtered out mixes with water - Become urine - Ureters carry urine out of the kidneys.
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[A]: Blood carried into kidney by the renal artery

[Q]: What is the missing first step of the following process: - Embryo is C - Embryo grows and develops into a fetus inside the woman's womb - The fetus is born - Begins to grow and develop through infancy and childhood - In the teenage years the human experiences puberty - Reaches sexual maturity - At 18 the human becomes an adult - Adult may procreate continuing the cycle.
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[A]: A man and woman mate

[Q]: What is the missing first step of the following process: - Once in the lungs, oxygen is moved into the bloodstream and carried through your body - At each cell in your body, oxygen is exchanged for a waste gas called carbon dioxide - Your bloodstream then carries this waste gas back to the lungs where it is removed from the blood stream and then exhaled - Your lungs and respiratory system automatically perform this vital process, called gas exchange -
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[A]: He air we breathe contains oxygen and other gases

[Q]: What is the missing first step of the following process: - The sediments become glued together - The glued together parts become hard like cement - The sediment becomes a big rock - The rocks erode slowly - The rocks come apart - The rocks become smaller rocks - The rocks continue to erode into smaller rocks - The process starts again.
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[A]:
Minerals fill spaces between bits of sediment