The depicted diagram represents the effect of sewage discharge on some important characteristics of the river

• A

  Peak A – Sharp increase in BOD, the disappearance of clean water organisms.

  Peak B – Increase in dissolved oxygen, the reappearance of clean water organisms.

• B

  Peak A – Increase in dissolved oxygen, the reappearance of clean water organisms.

  Peak B- Sharp decline in dissolved oxygen disappearance of clean water organisms.

• C

  Peak A – Sharp increase in BOD, appearance of clean water organisms.

  Peak B – Increase in dissolved oxygen, the disappearance of clean water organisms

• D

  Peak A – Increased number of anaerobic bacteria, the disappearance of clean water organisms.

  Peak B – Sharp decline in dissolved oxygen, the reappearance of clean water organisms.