Modern day intense crop production means the application of greater and greater amounts of nitrogen fertilizers. this is turn means more nitrogen in the atmosphere which then leads to

More nitrogen in the atmosphere leads to NITRIC ACID RAIN.
When nitrogenous fertilizers are used on the farm, some gases are released into the atmosphere including nitric oxide. These gases rises up into the atmosphere, mix with rainfall.
 Nitric oxide react with rainfall to form nitric acid and it falls as acidic rain.

Small hydrophobic molecules and gases like oxygen and carbon dioxide cross membranes rapidly. Small polar molecules, such as water and ethanol, can also pass through membranes, but they do so more slowly.

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Explanation: