Answer:
Its D :)
<em>Or not i haven't done this in a while-</em>
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.
Mercury naturally exists in Liquid state.
On Condensing it can exist in Solid state as well.
Hope it helps...
Regards;
Leukonov/Olegion.
