Earthquakes are __1__；thousands of them happen each day.But most are too weak to feel.During a __2__ earthquake，there is often a great noise first.Then the earth __3__ terribly；many houses __4__ down.Railway tracks break and trains go __5__ lines；a great many factories are __6__；thousands of deaths are caused，and many more lose homes...__7__ the great damage and deaths caused by the earthquake __8__，other disasters such as fires often __9__.More buildings are destroyed and more __10__ are caused.
It is well known of the __11__ of a possible earthquake，and for centuries man has been making researches on earthquakes.More than 2,000 years ago，__12__，a Chinese scientist named Zhang Heng __13__ a machine which could find out from which __14__ the seismic (地震的) waves had come，and this machine is still __15__ by scientists today.Now we know much more about earthquakes and __16__ they happen，but we still cannot __17__ exactly when and where an earthquake will happen，and cannot __18__ it from happening.So earthquakes are among the __19__ disasters in the world.
No one can stop natural earthquakes.__20__，scientists can help stop earthquakes destroying whole cities and causing too many deaths.
1．A.common B．unusual
C．strange D．familiar
2．A.real B．weak
C．big D．small
3．A.moves B．shakes
C．jumps D．breaks
