Water pollution is caused due to

Given below are two statements:
Statement $I$: Chlorofluorocarbons breakdown by radiation in the visible energy region and release chlorine gas in the atmosphere which then reacts with stratospheric ozone.
Statement $II$: Atmospheric ozone reacts with nitric oxide to give nitrogen and oxygen gases,which add to the atmosphere.
For the above statements choose the correct answer from the options given below :

What steps should be taken to reduce the production of acid rain?

Which of the following is a gaseous pollutant?

Fill in the blanks:
$(1)$ Hydrocarbon compounds are made from ........ and ........ .
$(2)$ ........ has a capacity to stop the flow of oxygen.
$(3)$ ........ is formed by attaching carbon monoxide with hemoglobin in blood.

The concentration of fluoride,lead,nitrate and iron in a water sample from an underground lake was found to be $1000 \ ppb, 40 \ ppb, 100 \ ppm$ and $0.2 \ ppm,$ respectively. This water is unsuitable for drinking due to high concentration of: