People living in West Bengal suffer from black foot disease. This is caused by the contamination of groundwater with which of the following?

The increase in the concentration of toxic substances at successive trophic levels is known as ....

Match the columns:

Column-$I$	Column-$II$
$(1)$ Mercury	$(a)$ Low blood pressure,blindness
$(2)$ Lead	$(b)$ Hyperkeratosis,liver cirrhosis
$(3)$ Arsenic	$(c)$ Bone deformation,testicular atrophy
$(4)$ Cadmium	$(d)$ Abdominal pain,haemolysis
	$(e)$ Anaemia,convulsions

The electrostatic precipitator can remove over . . . . . . particulate matter. (in $;\%$)

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?

$A$ location with luxuriant growth of lichens on the trees indicates that the