The formation of the channel is initiated when electrons surge from
the cloud base toward the ground. When a stream of these negatively
charged electrons comes within 100 meters of the ground it is met by
a stream of positively charged particles that comes up from the ground.
When the negatively and positively charged streams meet, a complete
channel connecting the cloud and the ground is formed. The channel
is only a few centimeters in diameter, but that is wide enough for
electrons to follow the channel to the ground in the visible form of
a flash of lightning. The stream of positive particles that meets the
surge of electrons from the cloud often arises from a tall pointed
structure such as a metal flagpole or a tower. That is why the subsequent
lightning that follows the completed channel often strikes a tall
structure.
Which of the following claims about lightning strikes can be
inferred from paragraph 5 ?
1.During a lightning strike the diameter of the channel the electrons
follow is considerably enlarged beyond a few centimeters
2.A building is unlikely to be hit by lightning unless it is at least
100 meters tail
3.A building is hit by a lightning strike because the building itself
has first determined the path the lightning then takes to it
4.The light of a lightning strike first appears at the point where
the streams of negative and positive particles meet
答案就是第四個 可是我找不出是從哪裡推出來的
可以麻煩解答一下嗎?! 謝謝
--
the cloud base toward the ground. When a stream of these negatively
charged electrons comes within 100 meters of the ground it is met by
a stream of positively charged particles that comes up from the ground.
When the negatively and positively charged streams meet, a complete
channel connecting the cloud and the ground is formed. The channel
is only a few centimeters in diameter, but that is wide enough for
electrons to follow the channel to the ground in the visible form of
a flash of lightning. The stream of positive particles that meets the
surge of electrons from the cloud often arises from a tall pointed
structure such as a metal flagpole or a tower. That is why the subsequent
lightning that follows the completed channel often strikes a tall
structure.
Which of the following claims about lightning strikes can be
inferred from paragraph 5 ?
1.During a lightning strike the diameter of the channel the electrons
follow is considerably enlarged beyond a few centimeters
2.A building is unlikely to be hit by lightning unless it is at least
100 meters tail
3.A building is hit by a lightning strike because the building itself
has first determined the path the lightning then takes to it
4.The light of a lightning strike first appears at the point where
the streams of negative and positive particles meet
答案就是第四個 可是我找不出是從哪裡推出來的
可以麻煩解答一下嗎?! 謝謝
--
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