The Bhopal gas tragedy in $1984$ was caused by the leakage of which gas?

At what level does noise become harmful noise pollution?

Increased concentration of $DDT$ affects birds by:

What is the full form of the following terms?
$(i)$ $PPM$
$(ii)$ $PPB$

It is a common practice to plant trees and shrubs near the boundary walls of buildings. What purpose do they serve?

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.