$pH$ value for acid rain will be

Which of the following gases is not a greenhouse gas?

Match List-$I$ and List-$II$:

List-$I$	List-$II$
$(a)$ Carbon monoxide	$(i)$ Carcinogenic
$(b)$ Sulphur dioxide	$(ii)$ Metabolized by pyrus plants
$(c)$ Polychlorinated biphenyls	$(iii)$ Haemoglobin
$(d)$ Oxides of nitrogen	$(iv)$ Stiffness of flower buds

Choose the correct answer from the options given below:

Given below are two statements.
Statement $I$: The non-biodegradable fly ash and slag from the steel industry can be used by the cement industry.
Statement $II$: The fuel obtained from plastic waste is lead-free.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which is the greatest source of air pollution these days?

Dissolved oxygen is essential for aquatic life. What are the reasons responsible for the depletion of dissolved oxygen in water?