Question

Many people think the search for cleaner energy leads only to renewable resources like sun, wind and water. But it __48__ leads to a fossil fuel. Natural gas is considered __49__ cleanest of the fossil fuels, the fuel created by plant and animal remains over millions __50__ years. Burning it releases fewer pollutants __51__ oil or coal. The gas is mainly methane (甲烷). It produces half the carbon dioxide of other fossil fuels. So __52__ may help cut the production of carbon gases linked to climate change.

Russia is first in __53__ are called "proved reserves" of natural gas. The United States is sixth. Over the years, big oil __54__ gas companies recovered much of the easily reached supplies of gas in America. They drilled straight down into formations where gas collects. __55___these supplies were used up, big drillers looked for similar formations in other countries.

Answer 1

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