Example 1:

　　Oceanography has been defined as "The application of all sciences to the study of the sea " Before the nineteenth century ,scientists with an interest in the sea were few and far between .Certainly Newton considered some theoretical aspects of it in his writings ,but he was reluctant to go to sea to further his work .

　　For most people the sea was remote , and with the exception of early intercontinental travelers or others , who earned a living from the sea, there was little reason to ask many questions about it ,let alone to what lay beneath the surface , The first time that the question "What is at the bottom of oceans "? had to be answered with any commercial consequence was when the laying of a telegraph cable from Europe to America was proposed. The engineers had to know the depth profile ( 轮廓) of the route to estimate the length of cable that had to be manufactured.

　　It was to Maury of US Navy that the Atlantic Telegraph Company turned, in 1853 , for information on this matter. In the 1840s,Maury had been responsible for encouraging voyages during which soundings (试探) were taken investigate the depths of the North Atlantic and Pacific Oceans. Later, some of his findings aroused much popular interest in his book The Physical Geography of the Sea.

　　The cable was laid , but not until 1866 was the connection made permanent and reliable. At the early attempts, the cable failed and when it was taken out for repairs it was found to be covered in living growths, a fact which defied contemporary scientific opinion that there was no life in the deeper parts of the sea.

　　Within a few years oceanography was under way. In 1872　　 Thomson led a scientific expedition, which lasted for four years and brought home thousands of samples form the sea. Their classification and analysis occupied scientists for years and led to a five -volume report, the last volume being published in 1895 .

　　This passage is mainly about_____________.

　　A) the beginnings of oceanography

　　B) the laying of the first undersea cable

　　C) the investigation of ocean depths

　　D) the early intercontinental communications

　　本题问及全篇的中心思想。通过快读（skimming ）我们知道这是一篇叙述"海洋学"的文章。第一段谈的是关于"海洋学"的定义；第二段是讲19世纪前对海洋感兴对趣的科学家不多；第三段谈到由于有人提了铺设海底电缆，人们才开始研究"海底深处究竟是什么"；第四段说Maury考察北大西洋和太平洋的发现引起广泛的注意；第五段讲修筑海底电缆过程中发现大量的海洋生物；最后一段是海洋学研究的成果。可风全篇主要是讲海洋学的研究是如何开展起来的，所以正确答案是A）。文章有好几个地方谈到铺设海底电缆B）和越洋通讯（D），但都是围绕着海洋学这条主线的。至于C)，测量海洋深度，只是一个细节，不可能是文章的中心意思。