These radio signals were heard first in 1967．They were coming from a point in th

These radiosignals were heard first in 1967．They were coming from apoint in the sky where there were no known stars．They were coming veryregularly too：once in just about a second．It was as if they werecontrolled by a clock．

   The scientists who heard thesignals did not tell anybody else．They were rather afraidto tell in case they frightened people．The signals were comingfrom a very small body—no bigger，perhaps，than theearth．Was that why no light could be seen from it? Or were the signals comingfrom a planet that belonged to some other star?

  There was no end to the questions．but thescientists kept the discussion secret．“Perhaps there areintelligent beings out there，”they thought，“little greenmen who are trying to send messages to other planets，or to us!” Sothe news was not given to the newspapers．Instead，thescientists studied the signals and searched for others like them．

  Well, all that happened in 1967 and1968．Since then scientists have learned more about those strange，regular radiosignals．And they have told the story，of course．The signalsdo not come from a planet；they come from a newkind of star called “pulsar”．About a hundred otherpulsars have now been found，and most of them arevery like the first one．

  Pulsars are strong radio stars．They are thesmallest but the heaviest stars we know at present．A handful ofpulsar would weigh a few thousand tons．Their light—if they givemuch light—is too small for us to see．But we can be sure ofthis：no little green men are living on them．

1. How wasthe first pulsar discovered?

    A．Scientistsheard a new kind of radio signal．

    B．Scientistsheard radio signals coming from an unknown star．

    C．Scientistssearched the sky and saw it．

    D．Scientistsheard radio signals sent by little green men from a small planet．

2.What madethe scientists think that the signals might be a sign of intelligent life?

    A．Because theywere coming from a very small body．possibly a planet．

    B．Because theycouldn't see the body．

    C．Because itseemed that they were controlled by a clock．

    D．Because theycouldn't understand the messages sent by the intelligent beings．

3.Why didn'tthey report the news?

    A．Because theywere afraid of frightening people．

    B．Becausescientists wanted to keep their discoveries secret．

    C．Because thesignals were heard only once．

    D．Because theydidn't know if the signals were from a pulsar．

4. When didthey think it safe to report the news?

A．When everyonehad forgotten the signals．

B．When thesignals stopped．

C．When theywere tired of studying the signals．

D．When otherpulsars were discovered．

试题答案

答案：B;C;A;D