What is the missing first step of the following process: - Makes water acidic - Kills fish - Kills the soils in trees - Leaves are also harmed.
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Answer: Acid rain enters the atmosphere and lands

What is the missing first step of the following process: - Air reaches the lungs - The lungs absorb the oxygen from the air - The oxygen is transported by hemoglobin - Red blood cells are made of hemoglobin - Blood has a lot of red blood cells - The heart moves the blood throughout the body - Blood can bring the oxygen to different cells in the body.
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Answer: Air travels into the body

What is the missing first step of the following process: - Two types of proteins exist in filaments in the muscles - The filaments move when the brain instructs them to - The motion of the filaments cause the muscle to shorten and contract - Opposing pairs of muscles exist in order to provide the necessary range of motion.
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Answer:
Electrical signals in the brain travel through nerves to muscles