问题：

[单选,材料题] 第59题应选：

回答下面的题目：

UndergrOund Coal Fires

Coal burning deep underground in China, India and Indonesia is threatening the environment and human life, scientists have warned. These large scale 51 blazes ( 火焰 ) cause the ground temperature to heat up and kill surrounding vegetation, produce greenhouse gases and can 52 ignite ( 点燃) forest fires, a group of scientists told the annual meeting of the American Association for the Advancement of Science in Denver. The resulting 53 of poisonous elements like mercury can also pollute local water sources and soils, they warned.
"Coal fires are a global disaster," said Associate Professor Glenn Stracher of East Georgia Collage in Swainsboro, USA. But 54 few people know about them.
Coal can heat up on its own, and eventually catch fire and burn, if there is a continuous oxygen supply. The heat produced is not caused to 55 and under the right combinations of sunlight and oxygen, can trigger spontaneous ( 自发的 ) catching fire and burning. This can occur underground, in coal stockpiles, abandoned mines or even as coal is transported. 56 fires in China consume up to 200 million tons of coal per year, delegates were told. In 57 , the U.S. economy consumes about one billion tons of coal annually, said Stracher, 58 analysis of the likely impact of coal fires has been accepted for publication in the International Joomal of Acoal Ecology.. 59 underway, coal fires can burn for decades, even centuries. In the process, they release large 60 of greenhouse gases, poisonous fumes and black particles into the atmosphere.
The members of the panel discussed the 61 these fires may be having on global and regional climate change, and agreed that the underground nature of the fires makes them difficult to 62
Ultimately, the remote sensing and other techniques should allow scientists to 63 how much carbon dioxide these fires are emitting ( 释放 ). One suggested 64 of containing the fires was presented by Gary Colaizzi, of the engineering firm Goodson, which has developed a heat-resistant grout ( 灌浆 ), which is designed to be pumped into the coal fire to 65 the oxygen supply.
第51题应选：

A . Yet
B . Unless
C . Although
D . Once