Answer:
The mutations that were found in the parents were mostly somatic mutations
Step-by-step explanation:
It has been mentioned in the question that leukemia was mainly found in the persons who were directly exposed to the radiation and it was absent in their children so this fact suggests that the mutations that were found in the parents were mostly somatic mutations and thus they are not transferred to the children from their parents. As these mutations were induced due to exposure of radiation so it was induced mutation. And such induced mutations do not get inherited to the offspring.