We can reduce the air pollution in the following ways-:
i Planting trees to reduce the level of carbon dioxide.
ii. Getting our vehicles serviced well to reduce incomplete consumption of fuels.
iii. Saying no to crackers during Diwali celebrations.
iv. Walking to nearby places and saving fuel.

No, clear or transparent water is not always fit for drinking as it may have microorganisms and dissolved impurities which cannot be seen with naked eyes. These impurities and microbes may cause diseases. 

Pure air has 78% nitrogen, 21% is oxygen and carbon dioxide, argon, methane, ozone and water vapour are also present in very small quantities. Pure air has balanced quantity of all its constituent gases and it is free from harmful gasesand is fit for breathing.
On the other hand polluted air has unwanted gases and other suspended impurities like dust and smoke. It is unfit for breathing and has a harmful effect on both the living and the non-living. 

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To ensure the supply of clean water to all its residents the following measures can be taken :

(i) Strict laws should be enforced on industrial units, which dispose polluted water in water resources.

(ii) Open defecation in water resources by slum dwellers should be strictly prohibited.

(iii) The water supplied should be treated properly , made fit for use and  free from impurities and microorganisms. Chlorine tablets should be distributed for purification of water during rainy season.

(iv) People should be made aware and motivated to keep water resources clean.

Water gets contaminated by following ways :

(i) Disposal of sewage in rivers.

(ii) Throwing of chemicals which are harmful and poisonous in the water bodies by various industrial units.

(iii) Mixing of harmful chemicals used in agricultural process with ground water, making it unfit for consumption.