Global energy demand is expected to triple by mid-century. The earth is unlikely to run ou

t of fossil fuels by then, given its vast reserves of coal, but it seems unthinkable that we will continue to use them as we do now. It's not just a question of supply and price, or even of the disease caused by filthy air. The terrorist assault on the World Trade Center raises other scary scenarios: how much easier would it be to crack open the Trans-Alaska pipeline and how much deadlier would it be to bomb a nuclear plant than to attack a wind arm？

Skeptics may recall the burst of enthusiasm for conservation and renewable power when oil prices quadrupled in the 1970s. State-funded energy research and development surged, while tax incentives boosted solar, wind and other alternatives to petroleum and the atom. But when oil supplies loosened and prices dropped in the early 1990s, governments lost interest. In the state of California, subsidies evaporated, pushing wind companies into bankruptcy.

Clean energy has long way to go. Only 2.2% of the world's energy comes from "new" renewables such as small hydroelectric dams, wind, solar and geothermal. How to boost that share--and at what pace--is debated in industrialized nations--from Japan, which imports 99.7 % of its oil, to Germany, where the nearby Chernobyl accident turned the public against nuclear plants, to the U.S., where the Bush Administration has strong ties to the oil industry. But the momentum toward clean renewables is undeniable. How soon we reach an era of clean, inexhaustible energy depends on technology. Solar and wind energies are intermittent: When the sky is cloudy or the breeze dies down, fossil fuel or nuclear plants must kick into compensate. But scientists are working on better ways to store electricity from renewable sources.

While developed nations debate how to fuel their power plants, however, some 1.6 billion people--a quarter of the globe's population--have no access to electricity or gasoline. Many spend their days collecting firewood and cow dung, burning it in primitive stoves that belch smoke into their lungs. To emerge from poverty, they need modern energy. And renewables can help. From village-scale hydropower to household photovoltaic systems to bio-gas stoves that convert dung into fuel.

Ultimately, the earth can meet its energy needs without fouling the environment. "But it won't happen," asserts Thomas Johansson, an energy adviser to the United Nations Development Program, "without political will." To begin with, widespread government subsidies for fossil fuels and nuclear energy must be dismantled to level the playing field for renewables. Moreover, government should pressure utility to meet targets for renewable sources of energy.

The author's biggest worry about using nuclear energy is that ______.

A．it will do great harm to the inadequate reserves of coal

B．it is deadly if terrorists attack a nuclear plant

C．it will limit the development of many other alternatives

D．there will be a wider gap between developed and developing countries