According to the article, people named this stuff "flammable ice" because______

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问题 According to the article, people named this stuff "flammable ice" because______
  
Buried below the seabed around Japan, there are beds of methane, trapped in molecular cages of ice. In some places, the sediment covering these deposits of frozen water and methane has been eroded away, leaving whitish mounts of what looks like dirty ice rearing up out of the seafloor.
   Take a chunk of this stuff up to the surface and it looks and feels much like ice, except for a give-away fizzing sensation in the palm of your hand, but put a match to it and it doesn’t just melt, it ignites. Large international research programs and companies in Japan, among other countries, are racing to retrieve this strange, counter-intuitive substance — known as fiery ice — from beneath the seafloor to use its methane for fuel. If all goes to plan, they may even start extraction by the end of the next decade. But the journey so far has been far from smooth.
   There’s no doubt that methane hydrates could offer a major source of fuel, with recent estimates suggesting they constitute about a third of the total carbon held in other fossil fuels such as oil, gas and coal. Several nations, notably Japan, want to extract it. It is not hard to find, often leaving a characteristic seismic signature that can be detected by research vessels. The problem is retrieving that gas and bringing it to the surface.
   "One thing that’s clear is that we’re never going to go down and mine these icelike deposits, " says Carolyn Ruppel, who leads the US Geological Survey’s Gas Hydrates Project.
   It all comes down to physics. Methane hydrates are simply too sensitive to pressure and temperature to simply dig up and haul to land. They form at typically several hundred metres beneath the seafloor at water depths of about 500 metres, where pressures are much higher than at the surface, and temperatures are close to 0°C. Take them out of these conditions, and they begin to break down before the methane can be harnessed. But there are other ways to do it.

选项 A、The problem of extracting methane hydrates is retrieving methane gas and bringing it to the surface.
B、It is very easy to find methane hydrates.
C、Only Japan wants to extract methane hydrates.
D、Methane hydrates are a major source of fuel in Japan.

答案A

解析 细节判断题。根据原文“The problem is retrieving that gas and bringing it to the surface”可知,开采甲烷真正的挑战在于分离甲烷并将其输送到海面,A选项正确;B和C项均为过分曲解原文意思,原文说找到甲烷水合物并不难,但不意味着很容易找到,B选项错误;文中提到多个国家,尤其是日本希望开采甲烷水合物,而不是只有日本想要开采,C选项错误;由第三段开头“There’s no doubt that methane hydrates could offer a major source of fuel”可知,甲烷水合物可能会成为一种主要的燃料来源,并未提到甲烷水合物是日本的主要燃料来源,D选项错误。故选A。
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