Columnist: It is impossible for there to be real evidence that lax radiation standards that were once in effect at nuclear reactors actually contributed to the increase in cancer rates near such sites. The point is a familiar one: who can say if a particular case of cancer is due to radiation, exposure to environmental toxins, smoking, poor diet, or genetic factors. The argument's reasoning is most vulnerable to criticism on which one of the following grounds? ['The argument fails to recognize that there may be convincing statistical evidence even if individual causes cannot be known.', 'The argument inappropriately presupposes that what follows a certain phenomenon was caused by that phenomenon.', 'The argument concludes that a claim about a causal connection is false on the basis of a lack of evidence for the claim.', 'The argument ignores other possible causes of the increase in cancer rates near the nuclear reactor complexes.']