【单选题】

Remember global warmingBack inDecember, the threat of climate change was thundering, and the rich countries agreed to cut their carbon-dioxide and other green-house-related emissions. Since then, interest has cooled markedly, and manyEuropean countries are already running away from the promises they made so loudly a few months ago.But there has been much talk, and a bit of action, to encourage renewable (可更新的) energies such as wind, hydro, solar and all living organisms. These emit no greenhouse gases, but tend to cost more than coal, oil or gas.

The better, simpler idea is to remember that the easiest way to reduce something is to tax it—in this case, by taxing the carbon content of power. The dirtier the power, the more tax it would pay. So dirty coal would be more expensive than clean coal, which would see its price rise in relation to oil, which would be even more expensive compared to gas, which would lose some of its price advantage over renewables.
Unless a carbon tax was so huge as to be economically crippling, it would not remove the price differential (差别) between all renewables and fossil fuels.But it would narrow that gap, by fixing the differing environmental costs into the price—a useful principle in itself. It would also give renewable producers a strong incentive to cut costs, and fossil-fuel suppliers an motivation to clean their products.
Precedents suggest strongly that a carbon tax would be effective.But the disadvantage to carbon taxes is political.After almost a decade of trying, theEuropean Union gave up an attempt at aEuropean carbon tax last year. Germany’s ruling coalition is fighting against a proposed energy tax. InAmerica, politicians believe that even mentioning the notion is certain death.But many of the political objections could be met if a carbon tax were made up for the loss elsewhere, for example by lowering payroll or sales taxes. There is always suspicion when governments come up with clever new ways to tax, and rightly so. The response to that suspicion should be to win the argument, not to abandon it.
The standard of paying tax was ______.
A、that the more carbon content of power it contained, the higher tax one would pay
B、that oil would be more expensive than clean coal
C、that renewables would be most expensive of all
D、in the order that renewables are the most expensive while clean coal the cheapest