单项选择题

In spite of rising concern in the Northeast and Canada, Administration spokesmen have repeatedly insisted that nothing could really be done about acid rain and the industry-produced sulfur emissions until all the scientific facts were in. Suddenly last week, however, facts came raining down, in effect making further scientific debate on what mainly causes the problem all but irrelevant. 　　What brought about the downpour was a study commissioned by Presidential Science Adviser. The spokesmen plainly called for remedial action even if some technical questions about acid rain were still unanswered. "If we take the conservative point of view that we must wait until the scientific knowledge is definitive," said the spokesman, "the accumulated deposition and damaged environment may reach the point of ’’irreversibility’’." 　　When it rains, it pours. Next came a study from the National Research Council. Its definitive conclusion: reducing emissions of sulfur dioxide from coal-burning power plants and factories, such as these in the Midwest, would in fact significantly reduce the acidity in rain, snow and other precipitation(降水) that is widely believed to be worsening the life from fresh-water lakes and forests in the Northeast and Canada. The spokesman did not recommend any specific action. 　　A pair of remedial measures are already taken before Congress. A Senate committee recently approved a bill that would require reduction over the next decade of sulfur-dioxide emissions by 10 million tons in the States bordering on the east of the Mississippi. A tougher measure was introduced in the House ordering the 50 largest sulfur polluters in the U. S. to cut emissions substantially. To ease the Eastern coal mining industry, which fears a switch to low-sulfur Western coal, the bill requires the installation of expensive "scrubbers", devices for removing sulfur from the smoke, rather than an order that forbids high-sulfur fuel. Still, the legislation is being vigorously opposed by the coal industry and utilities, especially in the Mid-west, where heavy industries are battling to survive. In a survey also released last week, the Edison Electric Institute , an industry group, gravely predicted that electricity rates could rise as much as 50% if the emission-control legislation passed. 　　Government studies dispute these figures, but Congress has been suspended on acid-rain measures. Now, as a result of the academy study, supporters of the bills are more optimistic. Nevertheless, a major political battle is shaping up. The word "downpour" in the second paragraph most likely refers to