In the argument, the antinuclear activist presents two conclusions. The first is that his cause won a victory and the second is that the power industry acknowledges that they closed the plant because they couldn't operate it safely.
The nuclear manager takes issue with the second point, stating that it was economic considerations—not safety concerns—that forced the plant to close. The problem with the manager's argument is that he is essentially admitting that it was too expensive to operate the plant safely. He's assuming that economics and safety issues are mutually exclusive, but they actually aren't.
(E) says, "counts as purely economic considerations some expenses that arise as a result of the need to take safety precautions"
(E) describes the manager's flaw well. The manager takes economic issues as totally separate from safety concerns while at the same time admitting that they're directly tied to safety. Thus, (E) is the correct answer choice.
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