Hi, P. -

The argument is based on two essential statements, which can be paraphrased roughly as:

1) The government claims that the public's fears about nuclear power plants are unfounded.

2) The government has, however, taken an action (limiting liability) that is useful only if nuclear power plants do pose safety risks.

From these two statements, the editorial concludes that in spite of the government's claim, nuclear power plants do pose a safety risk. The conclusion is valid if the government may make empty claims, but does not take pointless actions. This is the meat of [D], which is therefore the right answer.

[C] is incorrect because it assumes too much; the argument does not state or imply that the power plants are safe "only because the financial security of those responsible for its operation depends on its being safe". Further, the editorial's point is that the government's action in limiting liability undermines its claim that power plants are safe, not that the action itself will make them less safe.

I hope this helps - please post again if you have further questions.

Best,
Lyn