试题出自试卷《北京科技大学2009年入学考试试题及解析》

What we see when we photograph the Sun is a huge glowing ball of gas. Underneath this hot and extremely bright photosphere lies other gas while, in the central parts of the Sun, atoms are continually being broken down and built up. In the center of the Sun it is just as if hundreds of thousands of hydrogen bombs were continually exploding, and the results of this reach the photosphere. This is why the photosphere shines so brightly and sends out x-rays and ultra-violet light. Yet sometimes dark spots appear on the photosphere and these “sunspots” are evidence of greatly increased activity below. When sunspots appear, great bursts of the longer radio waves are often received. These are a thousand times more intense than those which radio-astronomers normally receive and which comes from what is called “quiet” Sun, being radiated by the corona and the “chromospheres” that layer of not very bright gas which lies just above the photosphere.
These immense bursts of radio waves are usually accompanied by an intensely bright area of “flare” near a sunspot, and it is clear that they are caused by a sudden burst of thermal radiation from below the photosphere. The visible flare and the burst of radio waves are also accompanied by a burst of X-rays, ultra-violet rays, and atomic particles.
When there are sunspots but no flares accompanying them, the radio waves emitted by the “quiet” sun do not remain constant but began to fluctuate, and the radio signals gradually become stronger. These changes do not correlate with changes in the number of sunspots, although it has been emitted by the “quiet” Sun do not remain constant but began to fluctuate, and the radio signals gradually become stronger. These changes do not correlate with changes in the number of sunspots, although it has been found that the radio waves seem to be generated in the Sun’s atmosphere above the sunspots and not in the sunspots themselves. The changes in radio signals do, however, correlate with the calcium areas of the Sun’s spectrum.
Radio astronomy has helped considerably to increase our knowledge of the corona. Being visually very dim, the corona is hard to observe by optical means, even during total eclipses. During some eclipses it has been traced quite a long way from the Sun but was believed to extend no more than about two million miles at the most above the photosphere. Direct radiation of radio waves from the corona has been received during day light up to about 1.5 million miles. However, by examining a distant radio source as the Sun passes in front of it, it is possible to discover how far the corona extends by observing how the radio waves from the distant source are affected. It was in this way that Professors M. Ryle and A. Hewish at Cambridge University, England, found that the corona could be traced out to more than 6 million miles, and in the line of the Sun’s equator to 12 million miles or more. It has ever been suggested that the corona extends as far as the Earth itself.
1. A good title for this passage would be（ ）.
2. From the center out, the correct order of the sun’s layers is（ ）.
3. The photosphere is the（ ）.
4. The passage does not mention information dealing with the（ ）.
5. Professor M. Ryle and A. Hewish have found that the sun’s corona（ ）.