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Unformatted text preview: water arising from these flash floods likely also formed the odd teardropshaped “islands” (resembling the miniature versions seen in the wet sand of our beaches at low tide) that have been found on the plains close to the ends of the outflow channels. ■Judging from the width and depth of the channels, the flow rates must have been truly enormous―perhaps as much as a hundred times greater than the 105 tons per second carried by the great Amazon river. Flooding shaped the outflow channels approximately 3 billion years ago, about the same times as the northern volcanic plains formed.
12. Look at the four squares [■] that indicate where the following sentence could be added to the passage.
These landscape features differ from runoff channels in a number of ways.
Where would the sentence best fit?
13. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
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There is much debate concerning whether Mars once had water.
Answer choices ○Mars’ runoff and outflow channels are largescale, distinctive features that suggest that large quantities of liquid water once flowed on Mars.
○Although some researchers claim that Mars may once have had oceans, others dispute this, pointing to an absence of evidence or offering alternative interpretations of evidence. ○Various types of images have been used to demonstrate that most of Martian surface contains evidence of flowing water.
○The runoff and outflow channels of Mars apparently carried a higher volume of water and formed more extensive networks than do Earth’s river systems.
○There is very little evidence of liquid water on Mars today, and it is assumed that all the water that once existed on the planet is frozen beneath its surface.
○While numerous gullies have been discovered on Mars since 2000, many astronomers dismiss them as evidence that Mars once had liquid water. 261
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13. ○1, 2, 5 262
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This note was uploaded on 09/17/2013 for the course LANGUAGE 13DL208 taught by Professor Wang during the Fall '13 term at East China Normal University.
- Fall '13