As the earth formed, naturally occurring radioactive material

Naturally Occurring Radioactive Materials  (also known as NORM) are a wide range of radioactive isotopes that include elements such as carbon 14 and potassium 40, both of which are in the human body. But the main radioactive elements involved in oil and gas production are those found throughout Earth's crust. These elements include uranium and thorium and their respective byproducts, including radon gas.

Naturally Occurring Radioactive Materials (NORM) and Technologically EnhancedNaturally Occurring Radioactive Materials (TENORM) consist of materials, usually industrial wastes or by-products enriched with radioactive elements found in the environment, such as uranium, thorium and potassium and any of their decay ...

The correct answer to this question would be c