阅读下列短文，从每题所给的四个选项(A、B、C和D)中选出最佳选项。A 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. Mean- while, 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.