Red light being of longest wavelength scatters least and reaches our eye while blue colour scatters most.

DDT is a non-bio degradable pesticide and when sprayed, it finds its way to soil from where it enters the food chain, the concentration of DDT increases progressively as we go up the trophic level due to biological magnification.

When pesticides and other non-biodegradable chemicals enter the food chain, these get accumulated progressively at each trophic level and this is known as biological magnification.

The sky appears blue due to excessive scattering of blue light by the air molecules.

The limited supply of air leads to incomplete combustion of fuel, which in turn leads to the production of black smoke.