Which of the following cannot be degraded by natural processes?

(P) DDT (Q) Plastic materials (R) Heavy metals (S) Nuclear wastes

For instance, once discharged into the environment, pollutants like dichlorodiphenyltrichloroethane (DDT), plastics, heavy metals, many chemicals, and nuclear wastes, among others, are challenging to remove. These contaminants injure living things and cannot be broken down by natural mechanisms.