Which property of argon makes it useful for potassium-argon dating?

It decays into potassium.

It is an unstable element.

It remains trapped in rock.

It is useful only for dating newer roc

It is an unstable element.

Explanation:

Potassium argon dating is a radiometric dating method used for dating archeological materials like rocks. Geologists have used this method to date rocks that are over 4 billion years old. It is based on the fact that some of the potassium isotopes k-40, decays to gas Argon as Ar-40. It has been used to measure wide variety of ages.