下列关于对债券概念的理解中，正确的一项是( )

People living on parts of the south coast of England face a serious problem. In 1993, the owners of a large hotel and of several houses discovered, to their horror, that their gardens had disappeared overnight. The sea had eaten into the soft limestone cliffs on which they had been built. While experts were studying the problem, the hotel and several houses disappeared altogether, sliding down the cliff and into the sea. Erosion (侵蚀) of the white cliffs along the south coast of England has always been a problem but it has become more serious in recent years. Dozens of homes have had to be abandoned as the sea has crept farther and farther inland. Experts have studied the areas most affected and have drawn up a map for local people, forecasting the year in which their homes will be swallowed up by the hungry sea. Angry owners have called on the government to erect sea defenses to protect their homes. Government surveyors have pointed out that in most cases, this is impossible. New sea walls would cost hundreds of millions of pounds and would merely make the waves and currents go further along the coast, shifting the problem from one area to another. The danger is likely to continue, they say, until the waves reach an inland area of hard rock which will not be eaten as limestone is. Meanwhile, if you want to buy a cheap house with an uncertain future, apply to a house agent in one of the threatened areas on the south coast of England. You can get a house for a knockdown price but it may turn out to be a knockdown home.What is the cause of the problem that people living on parts of the south coast of England face?A．The disappearance of hotels, houses and gardens.B．The experts' lack of knowledge.C．The rising of the sea level.D．The washing-away of limestone cliffs. 点击查看答案

After inv estimating five residential gas explosions that killed four people in the Kansas City--Topeka area in 1988 and 1989, the National Transport action Safety Board has【C1】______ that automatic shut -off valves be required when home gas lines are installed or 【C2】______ The valves stop 【C3】 ______ and potentially【C4】______ surges in gas flow, such as would occur 【C5】______ a contractor hit and ruptured a pipe. The NTSB labeled the report' urgent',【C6】______ it doesn't rate the riskof surges high enough to ten consumers to【C7】______ $ t000 or so to dig up old lines and【C8】______ the $15 to $20 valve. A bigger【C9】______ to homeowners, says the NTSB, is the danger of slow 【C10】______ from pipe cur rosin,【C11】______ the valve would not prevent. Symptoms of a possible gas【C12】______ under your property include a sulfur smell and brown spots or dead【C13】______ in your yard. Call your gas company【C14】______ two of the Kansas City-area explosions【C15】______ had gas odors been【C16】______ And before【C17】______ start construction in your 【C18】______ , ask your gas company to【C19】______ mark the position of pipes【C20】______ your house.【C1】A．statedB．urgedC．thoughtD．stressed 点击查看答案