Question

which statement describes potassium - argon dating?
potassium - 40 decays into argon gas over time.
argon breaks down into other elements and compounds.
potassium - 40 becomes stable when trapped in rocks.
argon is unstable and will decay into potassium - 40 over time.

Explanation:

Potassium - 40 is a radioactive isotope. In potassium - argon dating, potassium - 40 undergoes radioactive decay and transforms into argon gas over time. This property is used to date rocks.

Answer:

Potassium-40 decays into argon gas over time.