Which of the following is a weightless pollutant?

Excess of which of the following in drinking water causes mottling of teeth?

What is the gradual increase in the concentration of toxicants at successive trophic levels called?

Foul smell in the water bodies of tanks,ponds,etc.,is due to:

Discuss briefly the following:
$(a)$ Greenhouse gases
$(b)$ Catalytic converter
$(c)$ Ultraviolet $B$

Select the correct option regarding algal bloom.
$I-$ Excessive growth of planktonic algae occurs due to the presence of high amounts of nutrients in water bodies.
$II-$ Algal bloom imparts a distinct color to the water bodies.
$III-$ Algal bloom causes deterioration of water quality and fish mortality.
$IV-$ All bloom-forming algae are highly toxic to humans and animals.