阅读理解

　　Bright comets(彗星) are a rare(罕见的)and beautiful sight. Though we think of them as members of the sun’s family, many comets go far beyond the orbits of the planets. As a rule they return once in a while to travel around the sun

　　A comet seems to be composed of gas, dust and ice. There is a great deal of solid, frozen material. As the mass gets near the sun, the outer frozen parts begin to melt(融化), and more gases form. The pressure of the sun’s radiation(放射) drives the dust and gases outwards in a long, streaming“tail”, perhaps several tails. For this reason the tail always points away from the sun. And when the comet moves farther from the radiation, the tail gets smaller and at last disappears.

　　We owe (把……归于)our knowledge chiefly to Sir Edmond Harley(1656－1742). He saw a very beautiful one in 1682, and it led him to study comets and their orbits.

　　Then he said,“The comet of 1682 was the same one that appeared in 1531 and again in 1607. It will return in 1758 or 1759.”

　　Harley died in 1742, but people waited and watched…And sure enough, Harley’s Comet arrived, big and bright, early in 1759. The comet was named:“Comet Harley”and it comes about every 75 years.

　　Last time it returned in 1986 and was watched by hundreds of millions of people. If you were one of them, I hope you will be lucky enough to watch it again next time it appears.

1．In what way are comets different from planets?

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A．They don’t travel round the sun.

B．They are not members of the sun’s family.

C．They are nearer to the sun than planets.

D．They go far beyond the sun than planets.

2．What is the long tail of the comet composed of (由……组成)?

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A．Gas, dust and ice.

B．Radiation of the sun.

C．Solid, frozen material.

D．Dust and gases.

3．

The reason why the tail of a comet always points away from the sun is that ________.

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A．it is getting nearer to the sun

B．the dust and gases are driven outward by the pressure

C．its outer frozen parts begin to melt

D．it is moving round the sun

4．Which of the following is right?

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A．Sure enough, Harley saw the comet arrive early in 1759.

B．Harley’s Comet returned in 1758 as Harley had expected.

C．Seventeen years after Harley’ death the comet returned.

D．We’ll see Comet Harley again in 75 years.

5．When will Comet Harley return next time?

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