单选题 The ocean bottom — a region nearly 2.5 times greater than the total land area of the Earth — is a great frontier that even today is largely unexplored and unknown. Until about a century ago, no one had access to the deep-ocean floor, which was hidden under waters over 3,600 meters deep. To humans, the deep-ocean bottom, totally without light but with intense pressures hundreds of times greater than at the Earth's surface, is an unfriendly environment, in some ways as forbidding and remote as loneliness of outer space.
Although researchers have taken samples of deep-ocean rocks and deposits for over a century, the first detailed global investigation of the ocean bottom did not actually start until 1968, with the beginning of the National Science Foundation's Deep Sea Drilling Project (DSDP). Using techniques first developed for the offshore oil and gas industry, the DSDP's drill ship, the Glomar Challenger, was able to maintain a steady position on the ocean's surface and drill in very deep waters, collecting samples of deposits and rocks from the ocean floor.
The Glomar Challenger completed 96 voyages in a 15-year research program that ended in November 1983. During this time, the drill ship covered 600,000 kilometers and took almost 20,000 samples of sea-bed rocks and deposits at 624 drilling sites around the world. The samples have allowed scientists to rethink what the planet looked like hundreds of millions of years ago and to calculate what it will probably look like millions of years in the future.
The samples have also produced information related to understanding the world's past climates. Deep-ocean deposits provide a climatic record tracing back hundreds of millions of years, because they are largely isolated from the erosion (侵蚀) and the intense chemical and biological activity that rapidly destroy much land-based evidence of past climates. This record provided insights into the patterns and causes of past climatic change — information that may be used to predict future climates.

单选题 The author refers to the ocean bottom as a "frontier" in Paragraph 1 because it ______.

单选题 Which of the following is true of the Glomar Challenger?

【正确答案】 D

【答案解析】细节题。由文章第二段第一句“the first detailed global investigation of the ocean bottom did not actually start until 1968, with the beginning of the National Science Foundation's Deep Sea Drilling Project (DSDP).”可知，随着国家科学基金会深海钻探计划的启动，对深海的详细探索是从1968年开始的，文章随后提到，进行这次深海探索的是“the DSDP's drill ship, the Glomar Challenger(格罗玛挑战者号)”。因此，[D]正确。

单选题 The Deep Sea Drilling Project was significant because it was ______.

【正确答案】 B

【答案解析】推理题。文章第二段第一句提到“Although researchers have taken samples of deep-ocean rocks and deposits for over a century, the first detailed global investigation of the ocean bottom did not actually start until 1968”，尽管研究者一个世纪以前就开始对海底岩石标本的研究，但详细的研究还是从1968年格罗玛挑战者号开始的，由此可推断出，深海钻探计划是第一次对深海海底的探索，因此，[B]正确。

单选题 The word "they" underlined in Paragraph 4 refers to ______.

单选题 The samples provide better information about the world's past climate because they ______.

【正确答案】 A

【答案解析】推理题。最后一段的第二句中提到“…because they(deep-ocean deposits) are largely isolated from the erosion and the intense chemical and biological activity that rapidly destroy much land-based evidence of past climates”，这些深海沉积物没有受到侵蚀，远离强化学物质和生物活动的影响，而正是这些因素毁掉了陆地上的证据。由此推断出，海底环境保护了深海沉积物。因此，[A]正确。