In this soil conservation method,several grasses are left out in the soil after the crop is harvested.

Soil conservation can be best achieved by having

For the best ecological balance,what percentage of the land mass of a country in the plains should be covered with forests (in $, \%$)?

Jhum cultivation:
$I.$ Also called as slash and burn agriculture,is the farming practice in North Eastern states of India.
$II.$ Farmers cut down the trees of forest and burn the plant remains.
$III.$ The ash is used as a fertilizer and the land is then used for farming or cattle grazing.
$IV.$ After cultivation,the land is left for several years,so as to allow its recovery.
Which of the statements given above are correct about Jhum cultivation?

Minerals,metals,and fossil fuels are which type of energy resources?

Which of the following changes would be likely to make terrestrial life on this planet impossible?