The correct option is A Pollutant
Pollutant is a substance which when introduced into the environment has undesired effects. Pollutant causes long- or short-term damage by changing the environmental factors. Some pollutants are biodegradable and therefore do not persist in the environment in the long term. However, the degradation products of some pollutants are themselves polluting such as the products DDE and DDD produced from degradation of DDT.