Answer:
more nitrogen compounds
Explanation:
when water is polluted by sewage many microorganisms is present so we can deduct the 1st ans.
as water is polluted the environment is not suitable so living organisms so unpolluted water has more fish than polluted.
there cant be more oxygen in a place where it s polluted coz plants which grow under water wont grow as it is polluted
more nitrogen compounds is the answer because nitrogen compounds are made due to the reactions in polluted water.
hope this helps,
