Final answer:
Irradiation of an unborn fetus can lead to genetic defects and possibly cancer, which may affect subsequent offspring due to DNA mutations in embryonic germ cells during critical development stages.
Step-by-step explanation:
Irradiation of the unborn fetus increases the risk of both cancer and genetic defects, with the latter potentially affecting subsequent offspring. Exposure to radiation during pregnancy can cause damage to DNA and result in mutations in the embryonic germ cells. These mutations, when taking place at such a crucial stage of development, would be replicated in multiple tissues and organs, leading to a high probability of severe impacts on the offspring, including possible genetic effects in subsequent offspring.
Radiation's long-term effects are more pronounced in cells that reproduce rapidly, which includes embryos. Therefore, the correct answer to the question is option b), 'Genetic; genetic effects in subsequent offspring.' Any amount of radiation may pose some level of risk, further underscoring the importance of protecting pregnant women from exposure to potentially harmful radiation levels.