Q.Which of the following is natural and human disturbance in ecology?

Environmental pollution is any undesirable change in the surroundings — air, water or soil — that has harmful effects on plants, animals and human beings. The agent responsible is called a pollutant: a solid, liquid or gaseous substance present in far greater concentration than its natural abundance, arising either from human activity or natural events. Pollutants originate at a source and are then transported by air or water, or dumped directly into soil. A key distinction is between degradable pollutants, which natural processes break down quickly (e.g., discarded vegetable matter), and slowly degradable or non-degradable pollutants such as DDT, plastics, heavy metals and nuclear waste, which persist for decades and are very difficult to remove once released. Because humans inhale roughly 12-15 times more air than the food they eat, even small concentrations of airborne pollutants matter more than similar levels in food.