In which of the following practices is the waste produced from one process used as a nutrient for another process?

Rice fields produce an important greenhouse gas. Name it.

Which of the following statements is correct?

$A$ large number of fish suddenly die in a lake near a village. Which of the following could be the reason for this?
$(a)$ Excessive use of urea and phosphate fertilizers in nearby fields.
$(b)$ Spraying of $DDT$ in the entire area.
$(c)$ The lake water has turned green and murky.
$(d)$ The population of phytoplankton in the lake has decreased,reducing the photosynthetic capacity.
Which two of the above reasons are responsible?

Select the correct option for 'Ecosan'.

At the beginning of the $20^{th}$ century,forests covered about $.....P.....$ of the land in India. By the end of the century,this had shrunk to $.....Q.....$.