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.

Oxidation is the addition of oxygen to a substance or the removal of hydrogen from a substance. The reaction in which heat energy is produced is called exothermic reaction.

As, light is scattered by the air molecules present in atmosphere and blue colour has shorter wavelength, so it is scattered most and the earth would appear blue.