Answer:
pollution is caused by 2 main sources.
1:natural sources 2:human beings.
human beings are the main pollutants,they are polluting land,water n air by their own actions n practices,even some where the natural sources of pollution like errosion of land is also subject to cause by us which is the result of deforestation,overgrazing of herds etc.
salinization and desertifications are the results of the advancments of human beings to some extends..polluted factory water contemnates river water whch is a source of fresh watr n many parts of the world.
traffic n transports pollut the air cause noise pollution and damages to the envirmnt and reflects as deseases n wearing off of the ozon lyr,.