question: What does a metastable isotope do to return to ground state from an excited state ?
answer: emitting a photon in the form of a gamma ray
turker_answer: A metastable isotope emits a photon in the form of a gamma ray to return to ground state from an excited state .
rule-based: A metastable isotope emits a photon in the form of a gamma ray to return to ground state from an excited state .