Before the nineteenth century, scientists with ah 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 them was little reason to ask many questions about it, let alone to ask what lay beneath the surface. The first time that the question what is at the bottom of the 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 of the route to estimate the length of cable that had to be manufactured.
It was to Maury of the U. S. Navy that the Atlantic Telegraph Company turned, in 1855, for information on this matter. In the 1840s, Maury had been responsible for encouraging voyages during which soundings were taken to 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 by 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 from the sea. Their classification and analysis occupied scientists for years and led to a five volume report, the last volume being published in 1895.
The passage implies that the telegraph cable was built mainly ______.

A. for Oceanographic studies
B. for military purposes
C. for business considerations
D. for investigating the depths of the oceans