请教36套ex3的第七题

merseysidechildUID: 3002352

A mysterious phenomenon is the ability of over-water
migrants to travel on course. Birds, bees, and other
species can keep track of time without any sensory cues  
Line from the outside world, and such ―biological clocks
5  clearly contribute to their ―compass sense.‖ For example,
they can use the position of the Sun or stars, along with
the time of day, to find north. But compass sense alone
cannot explain how birds navigate the ocean: after a flock
traveling east is blown far south by a storm, it will   
10  assume the proper northeasterly course to compensate.
Perhaps, some scientists thought, migrants determine
their geographic position on Earth by celestial navigation,
almost as human navigators use stars and planets, but this
would demand of the animals a fantastic map sense.   
15  Researchers now know that some species have a magnetic
sense, which might allow migrants to determine their
geographic location by detecting variations in the strength
of the Earth‘s magnetic field.         (157 words)

这里怎么就说明了compass sense不足以说明冒号后面的现象呢？

题目里也考到了这一点：
It can be inferred from the passage that if the   
  flock of birds described in lines 8-9 were  
  navigating  by  compass  sense  alone,  they  would,  after
the storm, fly
  (A) east  (B) north    (C) northwest
  (D) south  (E) southeast


答案是A。。。请教各位大牛该如何理解...谢谢

846136085UID: 2987171

compass sense只能判定方向，横跨大洋不能不能只靠方向

二爷08UID: 3228170

题目考取非

原文说仅仅依赖 compass sense 不能解释compensation这个现象，所以引出了 celestial navigation。

题目问 若仅仅依赖 compass sense 会咋样。 那么就是不做compensation，继续向east.....

Model_KTUID: 3062455

我弱弱的觉得 这个是不是物理的速度合成丫
就是本来是向东走的 然后有向南的storm作用力
所以就应该向东北方向走才能抵消
那如果不考虑这些而 compass  sense  alone的话，那就只是向东走了吧。。。

merseysidechildUID: 3002352

3# 二爷08
莫非是我理解错了？....我的理解是...这群小鸟一开始是向东飞的，然后让南风给吹偏了...于是乎它们compensate了一下...转头向东北方向飞...从而实现compensate...

还是说意思是这群鸟一开始就是朝着东北方向做了一个compensation？

霜满地UID: 3174396

你的理解应该是对的吧。。。compensation 就是指力学矢量合成后新的飞翔方向，如果仅仅靠鸟的定向感它们应该只会继续向东飞而不是做轨迹复原~

merseysidechildUID: 3002352

6# 霜满地
懂了...忽略了after the storm...谢谢..