Tidal action is a very complicated phenomenon involving many factors all of which must be considered to predict tide in any one place and at any one time. The alternate rise and fall of the surface of the seas and the ocean is mainly caused by the attractive force of the moon alone. When the attraction is great, the tide is high; and conversely when the attraction is minimal, the tide is low. Between the high tide and the low tide is a period of a little over six hours, being called during its rise a flood tide, and during its fall an ebb tide.
The sun also exerts its effect on the tide, being a little less than half as much as the moon, although it’s mass is so much greater. When the moon and the sun are horizontal, the highest high tide occurs and when they are vertical the lowest low tide takes place.
The wind also plays an important part in the modification of the normal rise and fall of the tide. Thus these factors affect each other, either distracting or adding to the attractive forces to add or subtract from the height of the tide. But the tides still move inexorably on, rising twice a day, getting little later each day and posing a problem of correctly predicting their heights and lows.
46. The principal ideas of the article concerns（ ）.
47. Which of the following factors is NOT mentioned as affecting the tide?
48. It can be concluded from the article that the attraction of the sun is（ ）.
49. If the first high tide takes place at 1:00 a. m. the next high tide will probably take place at（ ）.
50. According to the article, it is clear that the role of the moon（ ）.
问题1选项
A.the attraction of the sun and the moon
B.tidal waves
C.the sun, the moon and the wind
D.features which affect the tide
问题2选项
A.The sun
B.The moon
C.The winds
D.The depth of the ocean
问题3选项
A.less than half that of the moon
B.more than half that of the moon
C.more than that of the moon
D.less than twice that of the moon
问题4选项
A.7:20 a.m.
B.8:00 a. m.
C.1:45 p. m.
D.high noon
问题5选项
A.is not as important as that of the wind
B.is less than that of the sun
C.causes the alternate rise and fall of the surface of the seas
D.has little influence on the tide
第1题:D
第2题:D
第3题:A
第4题:C
第5题:C
46. 主旨大意题。根据本文的第一句Tidal action is a very complicated phenomenon involving many factors all of which must be considered to predict tide in any one place and at any one time.（潮汐运动是一个非常复杂的现象，涉及了很多必须考虑的因素，来预测在任何地方和任何时间发生的潮汐运动。）接着详细介绍了产生潮汐的主要因素。A选项“太阳和月亮的引力”；B选项“潮汐波”；C选项“太阳、月亮、风”，ABC选项只是文中讲到的一些片面信息，不能作为整体概述。D选项“引起潮汐的特征”正确，本文主要列举了引起潮汐的一些因素。故选D。
47. 客观细节题。影响潮汐的因素可以看到第一段的第二句The alternate rise and fall of the surface of the seas and the ocean is mainly caused by the attractive force of the moon alone.（海洋表面的交替上升和下降主要是由月球的吸引力引起的。）第二段第一句The sun also exerts its effect on the tide.（太阳也会对潮汐有影响。）第三段第一句The wind also plays an important part in the modification of the normal rise and fall of the tide.（风也在影响潮汐正常上升和下降的过程中起着重要的作用。）唯独D选项“海洋的深度”并未有提及，故选D。
48. 推理判断题。定位在第二段第一句The sun also exerts its effect on the tide, being a little less than half as much as the moon, although its mass is so much greater.（太阳对潮汐也发挥了作用，虽然它的体积狠大，但是，它的作用还不及月亮作用的一半。）由此可知，太阳对潮汐的影响比月亮的少了一半。由此可知A选项“不及月球的一半”正确。即可排除B选项“超过月亮的一半”和C选项“比月球还要多”，D选项“比月球的影响少两倍”错误。故选A。
49. 推理判断题。定位在第一段的最后一句Between the high tide and the low tide is a period of a little over six hours, being called during its rise a flood tide, and during its fall an ebb tide.（高潮和低潮之间的时间差超过六小时，上升时被称之为涨潮，下降时被称之为退潮。）题目中第一次的高潮发生在上午1点，那么接下来会有超过6个小时的低潮期，下次高潮的时间就还需要再加上6个小时。由此推理，时间要超过12个小时。同理可排除ABD选项。故选C。
50. 客观细节题。定位在第一段的第二句The alternate rise and fall of the surface of the seas and the ocean is mainly caused by the attractive force of the moon alone.（海洋表面的交替上升和下降主要是由月球的吸引力引起的。）A选项“不像风那么重要”，B选项“比太阳的影响小”，D选项“对潮汐的影响很小”均表述有误。选项C“导致海平面交替上升和下降”正确。故选C。
