The radiation absorbed by someone during an ordinary commercial airline flight is no more dangerous than that received during an ordinary dental X-ray. Since a dental X-ray does negligible harm to a person, we can conclude that the radiation absorbed by members of commercial airline flight crews will also do them negligible harm. A flaw in the argument is its failure to consider that
A: there may be many forms of dangerous radiation other than X-rays and the kinds of radiation absorbed by members of commercial airline flight crews
B: receiving a dental X-ray may mitigate other health risks, whereas flying does not
C: flying at high altitude involves risks in addition to exposure to minor radiation
D: the longer and the more often one is exposed to radiation, the more radiation one absorbs and the more seriously one is harmed
Choose A, B, C or D as your solution.
D