In which state/country are Ecosan toilets not found?

Consider the following reasons for the massive fish mortality observed in a lake near a village within a few days:
$(1)$ Excessive use of urea and phosphate fertilizers in nearby crops.
$(2)$ Spraying of $DDT$ using aircraft.
$(3)$ The lake water turned green and foul-smelling.
$(4)$ Initial decrease in phytoplankton in the lake leads to a maximum decrease in photosynthesis.
Which of the above reasons are responsible for the massive fish mortality?

Human activities interfere with the carbon cycle. List any two such activities.

In Arcata,the integrated wastewater treatment was developed by creating a series of $6$ connected marshes. Its function is $............$

Terracing is done in

At the beginning of the twentieth century,forests covered about ........... percent of the land of India. By the end of the century,it shrunk to ............. percent.