[Q]: What is the missing first step of the following process: - The oxygen travels to the lungs through the windpipe - The air sacs in the lungs send the oxygen into the blood stream - The carbon dioxide in the blood stream is transferred to the air sacs - The lungs expel through the nose or mouth back into the environment.
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[A]: You breathe oxygen into your body through the nose or mouth

[Q]: What is the missing first step of the following process: - The blood is passed through the nephrons in the kidneys - The kidneys filter the waste from the blood - The clean blood is circulated out of the kidneys - Excess water and waste is expelled from the kidneys in the form of urine.
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[A]: The kidneys receive blood through the renal artery

[Q]: What is the missing first step of the following process: - The star burns until it runs out of fuel - The star can no longer support its weight - The layers of hydrogen press down on the core - The core gets smaller and smaller under the pressure - The pressure causes gravity to get stronger - The gravity becomes so powerful that nothing can escape it - Anything that gets close to it, is drawn into it by its gravity - Light is drawn into it - Light can not escape -
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[A]: Stars burn mass

[Q]: What is the missing first step of the following process: - You fill the tray with warm water - You carefully place the tray on an even surface in a freezer that is at least 32 degree Farhenheit, the freezing point of water - The water begins to get colder until it starts to freeze solid - The water expands as it freezes, one of the few liquids that has greater volume as a solid - Because you used warm water, the gasses in the water had evaporated out, so you will have nice clear ice cubes without cracks from the trapped gasses -
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[A]:
You find an empty ice cube tray