28. The writer of this passage would possibly not agree with which of the following？ (A) The long-term effects of additional radiation should be considered before whole populations begin space travel. (B) Mutation rates can be tripled through low levels of radiation in each generation. (C) Prenatal and postnatal development are affected every little by the physical environment. (D) There is little danger of genetic mutation from medical treatment which has been neglected by the general public.