A large quantity of urban sewage is drained into nearby village river. Which among the given conditions would happen after mixing of sewage into the river?
(i) $\quad$Biochemical oxygen demand (BOD) of receiving water body increases.
(ii)$\quad$ Dissolved oxygen of receiving water body decreases.
(iii) $\quad$It will not cause mortality among fishes and other aquatic creatures.
(iv) $\quad$It will lead to nutrient enrichment of receiving water body.