The correct answer is: Thorium.
Thorium is a naturally occurring radioactive element that is found in rocks and soil. It can be released into the environment through mining, processing, and use of thorium-containing products. Thorium can also be released into the environment through natural processes, such as volcanic eruptions.
Thorium can cause radioactive pollution when it is released into the environment. Thorium can be absorbed by plants and animals, and it can also be inhaled or ingested by humans. Thorium can accumulate in the body, and it can cause cancer and other health problems.
In 2011, there was a radioactive pollution incident along the coast of Kerala, India. The incident was caused by the release of thorium from a thorium mine. The release of thorium caused contamination of the soil, water, and air. The contamination caused health problems for people who lived in the area.
Plutonium, zinc, and radium are also radioactive elements, but they are not as common as thorium. Plutonium is a man-made element that is used in nuclear weapons. Zinc is a common metal that is used in many products. Radium is a naturally occurring radioactive element that is found in some minerals.
Plutonium, zinc, and radium can also cause radioactive pollution when they are released into the environment. However, they are not as common as thorium, and they are not as likely to cause radioactive pollution.