If one curie of cobalt 60 is compared to one curie of Ir-192, what can be said about their disintegration rates?

The correct understanding in this scenario is that both one curie of cobalt-60 and one curie of iridium-192 will have the same number of disintegrations per second. A curie is defined as a quantity of radioactive material that decays at a rate of 3.7 x 10^10 disintegrations per second. Thus, regardless of the nuclide, one curie signifies that there will be 3.7 x 10^10 disintegrations occurring every second for both isotopes.

Although cobalt-60 and iridium-192 are different isotopes with distinct half-lives and behaviors, when expressed in curies, their activity (the rate of disintegration) is standardized. This means that despite potential differences in their stability or specific decay characteristics, at the curie level, they are equivalent regarding disintegration rates.

The other options touch on aspects such as decay rates, radioactivity, and stability, but they do not apply here in the same context, as the curie measurement inherently ensures equivalence in disintegration rates across different radioactive materials.