The most appropriate model of radioactive decay from the given options is popping a bag of popcorn.
This analogy fits because, similar to radioactive decay, the popping of popcorn occurs randomly and independently for each kernel, and once a kernel pops, it cannot revert back to its original state, mirroring the irreversible nature of radioactive decay. The other options do not exhibit the same randomness and irreversibility as clearly as the popcorn analogy.