Smog is caused by the presence of which of the following?

What would have happened if the greenhouse gases were totally missing in the earth's atmosphere? Discuss.

Give brief information about the types of smog.

Provide the correct statement for the following: (Use $T$ for True and $F$ for False statements.) $(1)$ Plants obtain elements like carbon,hydrogen,and oxygen from air and water. $(2)$ Plants obtain elements like $N, P, K, Ca$ from the soil. $(3)$ Compound fertilizers contain nitrogen as ammonium nitrate,phosphorus as $PCl_3$,and potassium as $KO_2$. $(4)$ The use of $NPK$ fertilizers increases the production of crops and vegetables in the soil.

Global warming may result in

The concentration of dissolved oxygen $(DO)$ in cold water can go up to ......... $ppm$.