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

Which of the following gases causes depletion in the ozone layer?

Given below are two statements:
Statement $I$: An allotrope of oxygen is an important intermediate in the formation of reducing smog.
Statement $II$: Gases such as oxides of nitrogen and sulphur present in the troposphere contribute to the formation of photochemical smog.
In the light of the above statements,choose the correct answer from the options given below:

Explain why sometimes foaming is seen in river water near the place where sewage water is poured after treatment?

An increase in the concentration of $CO_2$ in the atmosphere will result in ........

Which of the following particle sizes is associated with lung diseases?