Which type of dam is used for sinking toxins like PCB?

The correct answer to the question regarding the type of dam used for sinking toxins like PCBs is Overflow Dam. An Overflow Dam is specifically designed to allow toxins and contaminants to flow over its surface while also containing the hazardous materials below. This is effective when dealing with substances that should not be exposed to the environment due to their toxic nature.

In the case of managing PCBs, an Overflow Dam facilitates proper containment and can be employed to control the release of contaminants, ensuring that they are safely managed and do not adversely affect surrounding ecosystems or groundwater. This design is crucial when considering the hazardous properties of PCBs, which are persistent in the environment and can lead to significant ecological and health risks.

The other types of dams mentioned, such as Simple, Constant Monitor, and Underflow Dams, do not specifically provide the same level of containment and management for hazardous materials like an Overflow Dam does, and thus would not be appropriate choices for the safe handling of toxic substances.