What do you understand by ppm ?
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PPM stands for "parts per million." It is a unit of measurement used to express the concentration of one substance in relation to a million units of another substance. It is commonly used to quantify the presence of pollutants in air.
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What do you understand by ozone depletion ?
What is a pollutant ?
State an advantage of CNG (Compressed Natural Gas).
State how CFCs break ozone layer.