Where was the attempt to treat wastewater by combining artificial and natural processes carried out?

Choose the correct option regarding the following statements:
$(1)$ $CO_2$ contribution in global warming is $60\%$.
$(2)$ Greenhouse effect occurs due to deforestation.
$(3)$ Due to the greenhouse effect,the present average temperature at the surface of the Earth is $15^oC$.
$(4)$ The amount of $DDT$ in small fish is $0.05\ ppm$.

Which is the main causative factor of desertification?

Which one of the following is not related to $5\; F's$ of the Chipko movement?

What are the side effects of heavy and constant grazing?

Polyblend is made using $..............$.