阅读下面的短文。每篇短文后面都有七句话，请根据短文的内容判断这些话是正确、错误，还是在短文中没有提到。每个试题计1分,共计7分。
　　 The Northern Lights
　　 The Sun is stormy and has its own kind of weather．It is so hot and active that even the Sun’s gravity cannot hold its atmosphere in check1! Energy flows away from the Sun toward the Earth in a stream of electrified particles that move at speeds around a million miles per hour2．These particles are called plasma，and the stream of plasma3 coming from the Sun is called the solar wind．The more active the Sun，the stronger the solar wind．
　　 The solar wind constantly streams toward the Earth，but don’t worry because a protective magnetic field surrounds our planet．The same magnetic field that makes your compass point north also steers the particles from the Sun to the north and south poles．The charged particles become trapped in magnetic belts around the Earth．When a large blast of solar wind crashes into the Earth’s magnetic field，the magnetic field first gets squeezed and then the magnetic field lines break and reconnect．4
　　 The breaking and reconnecting of the magnetic field lines can cause atomic particles called electrons trapped in the belts to fall into the Earth’s atmosphere at the poles．As the electrons fall to the Earth，they collide with gas molecules in the atmosphere，creating flashes of light in the sky．Each atmospheric gas glows a different color．Oxygen and nitrogen glows red and green and nitrogen glows violet-purple．As these various colors glow and dance in the night sky，they create the Northern Lights and the Southern Lights．
　　 Watching auroras is fun and exciting，but normally you can only see them in places far north like Alaska and Canada．The movement of the aurora across the sky is usually slow enough to easily follow with your eyes but they can also pulsate，flicker，or even move like waves．During solar maximum，5 auroras are seen as far south as Florida，even Mexico! 6
　　 Auroras often seem to be very close to the ground，but the lowest aurora is still about 100 kilometers above the ground，a distance much higher than clouds are formed or airplanes can fly．A typical aurora band can be thousands of kilometers long，a few hundred kilometers high，but only a few hundred meters thick．
　　 We hope you are able to travel to far north places like the Arctic Circle and see the Northern Lights at least once during your lifetime．We know you will never forget it!
　　词汇：
　　 electrify/I5lektrIfaI/v．使带电 plasma/5plAzmE/n．等离子体
　　 steer/stiE (r)/v．认驾驶；导向，引向 electron/I5lektrRn/n．电子
　　 collide/kE5laid/v．碰撞 molecule/5mClikju:l/n．分子
　　 aurora/C:5rC:rE/n．极光 pulsate/pQl5seit/v．跳动
　　 flicker/5flikE (r)/v．闪烁 Arctic/5B:ktik/adj．北极的
　　注释：
　　 1． The sun cannot hold its atmosphere in check：太阳无法控制它自己的大气层。hold ．．．in check是“控制，支配”，例如：
　　 He wants tO hold the company in chedk through the manager’s secretary．
　　他想通过经理的秘书控制公司。
　　 2． move at speeds around a million miles per hour：以约100万英里的时速运动。around＝about。
　　 3． the stream of plasma：等离子流
　　 4． the magnetic field first gets squeezed and then the magnetic field lines break and reconnect：首先，磁场受到挤压，接着磁场磁力线断开又闭合。
　　 5． During solar maximum：在太阳风暴达到最高峰的期间
　　 6． auroras are seen as far south as Florida，even Mexico!：位于极南面的佛罗里达州，乃至于墨西哥都能看到极光。far south意为“极南面”。

　练习：
　　 1． The Sun’s gravity is too weak to keep its plasma from flowing to the Earth．
　　 A Right B Wrong C Not mentioned
　　 2． The Earth is quite safe with a magnetic field surrounding it to protect it from the attack by the solar wind．
　　 A Right B Wrong C Not mentioned
　　 3． Some scientists are worrying about the possible disappearance of the Earth’s protective magnetic field in the future．
　　 A．Right B Wrong C Not mentioned
　　 4． The auroras are formed when the electrons falling into the Earth’s atmosphere at the poles and colliding with gas molecules in the atmosphere．
　　 A．Right B Wrong C Not mentioned
　　 5． You cannot see the Northern Lights unless you are in Alaska or Canada．
　　 A Right B Wrong C Not mentioned
　　 6． Tens of thousands of tourists take special trips to Norway and Sweden every year to watch the Northern Lights．
　　 A Right B Wrong C Not mentioned
　　 7． An aurora is generally close to the ground and is very long and thick．
　　 A．Right B Wrong C Not mentioned
　　答案与题解：
　　 1． B 题句的意思是：太阳的重力太弱，等离子逃离太阳，流向地球。这一说法与短文第一段第一、二句表达的内容不符。句子表达的重点不是太阳的重力太弱，而是太阳太热，其活动又太剧烈，造成等离子逃离太阳，流向地球。所以，答案是选项B。
　　 2． A 题句说地球相当安全，因为有磁场在高空包围着地球，将太阳风挡在地球大气层外面。题句表达的意思与短文第二段第一句传递的信息相符。虽然短文中没有用safe这个词，但是“don’t worry because a protective magnetic field surrounds our planet”包含了safe这层意思，所以选项A是答案。
　　 3． C 题句说，有些科学家担心包围地球起防护作用的磁场有一天会消失。短文中找不到这一信息，所以答案是C。
　　 4． A 短文第二、三段解释极光的成因。当强大的太阳风侵入地球磁场，磁场的磁力线会断开和闭合，等离子流的电子进入大气层，流向极地上空，与大气层的气体分子发生碰撞，发出极光。题句表达的意思与短文介绍的极光成因相符，所以答案是A。
　　 5． B 题句的说法明显与短文第三段的叙述不符。第四段介绍说，当在太阳风暴达到最高峰的期间，明亮的北极光甚至在位于极南面的佛罗里达州乃至墨西哥都能看到。所以答案是B。
　　 6． C 题句说，每年有几万游客专程前往挪威和瑞典观看北极光。短文中找不到这一内容所以答案是C。
　　 7． B 题句说极光通常很接近地面，又长又厚。这一说法有两点与短文第五段的介绍不符。第一点，极光不是接近地面，而是“似乎很接近地面(Auroras often seem to be very close to the ground)”，事实上，最靠近地面的极光离地面也有100公里。第二点，极光不厚，“only a few hundred meters thick”。所以答案是B。