What is the result of the presence of excessive nutrients in water bodies?

What is causing concern for the Taj Mahal?

In a polluted lake,the index of pollution is

Delhi is one of the most polluted cities of the world. Which of the following steps were taken by the government to reduce vehicular pollution in Delhi?
$I.$ Phasing out of old vehicles
$II.$ Use of unleaded petrol
$III.$ Use of low sulphur petrol and diesel
$IV.$ Use of catalytic converters in vehicles
$V.$ Applying stringent pollution level norms for vehicles
$VI.$ Switch over of public transport from diesel/petrol to $CNG$
Which of the statements given above are correct?

The Taj Mahal is threatened due to the effect of:

$A$: Biomagnification of $DDT$ can enhance the decline in bird population.
$R$: $DDT$ causes thinning of eggshells and their premature breaking by disturbing calcium metabolism.