Lower allowed concentrations of particulate matter released from factory smokestack is the action which should be taken to prevent pollutants.
What is a Pollutant?
This is a substance which produces undesirable effects in the environment and sources include automobiles etc.
Preventing pollutants that could directly start a positive feedback loop in the picture is by lowering allowed concentrations of particulate matter released from factory smokestack which is why option D was chosen.
Read more about Pollutant here https://brainly.com/question/1347424
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