标题: 新GRE阅读理解36套每日讨论--56（群178674184） [打印本页] 作者: 普渡哥 时间: 2011-11-2 09:16 标题: 新GRE阅读理解36套每日讨论--56（群178674184） Echolocating bats emit sounds in patterns characteristic of each species that contain both frequency- modulated (FM) and constant-frequency (CF) signals. The broadband FM signals and the narrowband 5 CF signals travel out to a target, reflect from it, and return to the hunting bat. In this process of transmission and reflection, the sounds are changed, and the changes in the echoes enable the bat to perceive features of the target. 10 The FM signals report information about target characteristics that modify the timing and the fine frequency structure, or spectrum, of echoes—for example, the target‘s size, shape, texture, surface structure, and direction in space. Because of their narrow 15 bandwidth, CF signals portray only the target‘s presence and, in the case of some bat species, its motion relative to the bat‘s. Responding to changes in the CF echo‘s frequency, bats of some species correct in flight for the direction and velocity of their moving prey. (150 words)
8. According to the passage, the information provided to the bat by CF echoes differs from that provided by FM echoes in which of the following ways? (A) Only CF echoes alert the bat to moving targets. (B) Only CF echoes identify the range of widely spaced targets. (C) Only CF echoes report the target‘s presence to the bat. (D) In some species, CF echoes enable the bat to judge whether it is closing in on its target. (E) In some species, CF echoes enable the bat to discriminate the size of its target and the direction in which the target is moving.
9. Which of the following best describes the organization of the passage? (A) A fact is stated, a process is outlined, and specific details of the process are described. (B) A fact is stated, and examples suggesting that a distinction needs correction are considered. (C) A fact is stated, a theory is presented to explain that fact, and additional facts are introduced to validate the theory. (D) A fact is stated, and two theories are compared in light of their explanations of this fact. (E) A fact is stated, a process is described, and examples of still another process are illustrated in detail.作者: wzg3511661 时间: 2011-11-2 22:20
DE作者: xiaomolaozhu 时间: 2011-11-29 13:08
D E， 呼唤版主公布答案哦作者: wshen0123 时间: 2011-12-1 00:16
da作者: ReDoGre 时间: 2011-12-1 22:46
CE作者: yifenliu1 时间: 2012-1-2 10:00
DA作者: poggyhand 时间: 2012-1-3 19:45
求答案作者: dudnju 时间: 2012-1-4 19:46
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