9．We all know that a strong earthquake attacked Japan on March 11th，2011．A number of people died in the natural disaster．All the people around the world felt sad for it．
An earthquake is a shaking of the ground caused by the sudden breaking of large parts of Earth's rocky outer shell（壳） and the sudden moving of Earth's rocky outer shell in opposite directions．Earthquakes are among the most powerful events on earth，and their results can be quite scary．A strong earthquake may send out energy 10，000times as great as that of the first atomic bomb（原子弹）．Rock movements during an earthquake can make rivers change their course（河道）．Earthquakes can cause great damage（破坏）and loss of life．Large earthquakes beneath（在…下方） the ocean can create great numbers of huge，harmful waves called tsunamis（海啸）that can get flood run for many miles．
Earthquakes almost never kill people directly．Instead，many deaths and hurts in earthquakes come from falling objects and the collapse（坍塌）of buildings，bridges，and other things．Fire coming from broken gas or power lines is another main danger during a quake．The force of an earthquake depends on how much rock breaks and how far it moves．Powerful earthquakes can shake the ground strongly for great distances．
Generally，a powerful earthquake occurs less than once every two years．At least 40 moderate（中等的）earthquakes cause damage so somewhere in the world each year．About 40，000 to 50，000 small earthquakes----large enough to be felt but not damaging----occur every year．
Nature cannot be overridden（藐视）！
根据短文内容选择最佳答案
46．The underlined word"occurs"in the passage means"A"in Chinese．
A．发生
B．发展
C．消失
47．From the passage，we know that an earthquake isB．
A．a powerful storm
B．a natural disaster
C．a kind of weather
48．PictureB shows how an earthquake happens on the Earth．
49．Which of the following is Not true according to the passage？C
A．strong earthquake may send out energy more than that of the first atomic bomb．
B．Generally，an earthquake almost never kill people directly．
C．There are about 4，000to 5，000small earthquakes every year．
50．What's the main idea of the passage？B
A．A strong earthquake in Japan．
B．Knowledge about earthquake．
C．Earthquakes and atomic bomb．
