Due to the increase in organic waste, BOD value increases and dissolved oxygen, making fishes die due to less oxygen.

(i) It can not be a reason for fishes die in water as there is nothing to do with a large number of mosquitoes. Both can live independently.

(ii) This second statement cannot be a reason too as it is a false statement. Due to organic waste, dissolved oxygen actually decreases.

(iv) It is a false statement as mud cannot be a reason for the clogging of gills. It is sedimentary pollution that causes fish gills to be clogged.