Explanation:
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The correct answer that would best complete the given statement above would be CELL RESPIRATION and FOSSIL FUELS. Carbon dioxide enters the atmosphere by animal and human cell respiration and the burning of fossil fuels. Human activities such as BURNING FOSSIL FUELS and RESPIRATION cycle carbon through the carbon cycle. Hope this is the answer that you are looking for.
Answer:
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B. Because of the presence of hydrogen sulphide in Brass, it combines with oxygen in air and form water, evaporates. So remained sulphide is colourless in air .So Brass gets discoloured in the air.