Biology 5090 · O Level · Effects of humans on ecosystems

Effects of humans on ecosystems — practice question

For what reason does the oxygen concentration in a river fall after sewage is discharged into it?

  • ALess oxygen is absorbed from the air.
  • BThere is a decrease in the number of plants.
  • CThere is an increase in the number of bacteria.
  • DThere is an increase in the number of fish.

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