2. 考研
  3. In the following text, some sentences have been removed. For Questions 41-45, choose the most suitable one from the list (A、B、C、

In the following text, some sentences have been removed. For Questions 41-45, choose the most suitable one from the list (A、B、C、

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问题 In the following text, some sentences have been removed. For Questions 41-45, choose the most suitable one from the list (A、B、C、D、E、F、G……) to fit into each of the numbered blank. There are several extra choices, which do not fit in any of the gaps. (10 points)

    At the end of the fifteenth century, celestial navigation was just being developed in Europe, primarily by the Portuguese. Prior to the development of celestial navigation, sailors navigated by "deduced"(or "dead") reckoning, hereafter called DR. This was the method used by Columbus and most other sailors of his era. In DR, the navigator finds his position by measuring the course and distance he has sailed from some known point. Starting from a known point, such as a port, the navigator measures out his course and distance from that point on a chart, pricking the chart with a pin to mark the new position. Each day’s ending position would be the starting point for the next day’s course-and-distance measurement.
    (41)______.
    The ship’s speed was measured by throwing a piece of flotsam over the side of the ship. There were two marks on the ship’s rail a measured distance apart. When the flotsam passed the forward mark, the pilot would start a quick chant, and when it passed the aft mark, the pilot would stop chanting. The pilot would note the last syllable reached in the chant, and he had a mnemonic that would convert that syllable into a speed in miles per hour. This method would not work when the ship was moving very slowly, since the chant would nm to the end before the flotsam had reached the aft mark.
    (42)______.
    Columbus was the first sailor (that we know of) who kept a detailed log of his voyages, but only the log of the first voyage survives in any detail. It is by these records that we know how Columbus navigated, and how we know that he was primarily a DR navigator.
    (43)______. If Columbus had been a celestial navigator, we would expect to see continuous records of celestial observations; but Columbus’s log does not show such records during either of the transatlantic portions of the first voyage.
    It has been supposed by some scholars that Columbus was a celestial navigator anyway, and was using unrecorded celestial checks on his latitude as he sailed west on his first voyage. (44)______. In other words, if Columbus were a celestial navigator, we would expect to see a sense of small intermittent course corrections in order to stay at a celestially determined latitude. These corrections should occur about every three or four days, perhaps more often.
    But that is not what the log shows. (45)______. Only three times does Columbus depart from this course: once because of contrary winds, and twice to chase false signs of land southwest. In none of these cases does he show any desire to return to a celestially-determined latitude. This argument is a killer for the celestial hypothesis.

A. Since DR is dependent upon continuous measurements of course and distance sailed, we should expect that any log kept by a DR navigator would have these records; and this is exactly what Columbus’s log looks like.
B. On his return voyage in 1493, Columbus started from Samaria Bay on the north coast of Hispaniola, and he made landfall at Santa Maria Island in the Azores. We know his entire DR courses and distances between these two points, since they’re recorded in his log.
C. In order for this method to work, the navigator needs a way to measure his course, and a way to measure the distance sailed. Course was measured by a magnetic compass. Distance was determined by a time and speed calculation: the navigator multiplied the speed of the vessel (in miles per hour) by the time traveled to get the distance.
D. On the first voyage westbound, Columbus sticks doggedly to his magnetic westward course for weeks at a time.
E. Could Columbus has corrected his compasses by checking them against the stars and thus avoids the need for course corrections? This would have been possible in theory, but we know that Columbus could not have actually done this.
F. Speed (and distance) was measured every hour. The officer of the watch would keep track of the speed and course sailed every hour by using a peg-board with holes radiating from the center along every point of the compass. The peg was moved from the center along the course traveled, for the distance made during that hour. After four hours, another peg was used to represent the distance made good in leagues during the whole watch. At the end of the day, the total distance and course for the day was transferred to the chart.
G. In that case, as magnetic variation pulled his course southward from true west, he would have noticed the discrepancy from his celestial observations, and he would have corrected it.
选项
答案C
解析 本题的关键在于理清文章的结构层次。本篇第一段提到了航位推算法(DR)，但只提到航海家通过在航海图上标出他航行的路线和距离来确定自己的位置，并未说明在海中航行时应该如何操作。第三段则讲到航海时用漂浮物测量船只每小时航行距离的具体办法。因此中间空白处肯定是有关在海中航行时应该如何测量船只航行的路线和距离的办法，而且应该为概要介绍。C项和F项都与此有关。但F项中的"the compass"出现的过于突兀，因上文并未提到。而根据下文，空白处肯定应出现"the compass"，C项中的"the compass"则引出的自然，能很好的衔接上下文。同时，"In order for this method to work"起到了承上启下的作用，因为"this method"指的是第一段所提到的"In DR，the navigator finds his position by measuring the course and distance he has sailed from some known point"，因此C项正确。
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