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

A. It decays into potassium.

B. it is an unstable element.

C. It remains trapped in rock.

D. It is useful only for dating newer rock.

Potassium-argon dating:-

Potassium-argon dating method is used for dating of very old archaeological rocks. Geologist are using this method of dating for rocks as old as 4 billion years old. This method is based on calculation of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Argon which is a noble gas, is a minor component of rock sample of geographical inyterest. When K decays to A r, it tremain trapped within the lattice as it is larger than the sapces between the other atoms in a crystal.

So the answer is C. It remains trapped in rock, this property of argon that is Ar make it useful for dating.