Identify the odd one out regarding the process of bio-magnification.

Assertion: Eutrophication shows an increase in productivity in water.
Reason: With increasing eutrophication,the diversity of the phytoplankton increases.

What measures, as an individual, would you take to reduce environmental pollution?

Consider the following statements about eutrophication:
$I.$ Eutrophication is the natural ageing of a water body by nutrient enrichment.
$II.$ The accelerated ageing of lakes due to sewage and agricultural and industrial wastes is called cultural or accelerated eutrophication.
$III.$ The plant nutrients responsible for eutrophication are nitrates and phosphates.
$IV.$ Phosphates and nitrates accelerate the growth of algae which utilize oxygen and may deoxygenate the water enough to kill the fish and other aquatic animals.
Which of the statements given above are correct?

$DDT$ residues are rapidly passed through the food chain causing biomagnification because $DDT$ is:

Phosphate pollution is caused by