题目内容：

The Iroquois named the great waterfall Niagara，which means “thunder of waters”．For people living near the falls in New York State or Canada，the thunder of falling water never stops—well，almost never．

On March 29，1848，the usually early signs of spring were coming to the Niagara Falls area．Snow was beginning to melt，and the air was losing its chilly bite .In the late afternoon，however，people began looking at each other as if to ask，“Something’s different．What is it?”Then they realized．The air was strangely silent；the thunder of the falls had stopped．

The people had been used to that dull roar(轰鸣)all their lives．They ran to the falls to see what had happened．To their astonishment，they found the riverbed above the falls empty．The  bottom of Niagara River lay exposed，with just a few trickles and puddles of water remaining among the rocks and mud．As word of the mysterious event spread，hundreds of people flocked to the scene—then thousands．After nightfall countless lanterns could be seen shining along the banks as New Yorkers and Canadians camped at the river’s edge，waiting to see the unusual sight at dawn．

Most who lived or came there were merely curious，but others felt a deep fear．Something unknown had upset the unchanging order of nature．What might happen next?

By the next day，5，000 people were there．Those who were brave began walking into the riverbed and to the base of the falls. They found arrowheads and other objects that had lain there for years—perhaps for ages．

For 30 hours the Niagara Rivet lay dry．Then came a distant roar，growing louder．People  scrambled up the banks．The waters rushed back，and all was as it had been．What had caused the river and the falls to stop? Only later did the people learn that a huge ice jam upstream had temporarily dammed the Niagara River．The fears were gone，but no one would forget the day the fails stopped．

1.What does the underlined words in Paragraph 2 mean?

A. The air was no longer able to bite．    B. The air was even colder than ever．

C. It was getting warmer．    D. It was not as cloudy as before．

2.Which of the following did people see at the riverbed and the base of the falls?

A. Remains of war．    B. Dead fish．

C. Large blocks of ice．    D. Strange animals．

3.What caused the falls to stop?

A. A newly man—made dam．    B. The ice that had piled up．

C. The rocks in upstream water．    D. The melting snow along the river．

4.It can be inferred from the passage that__________．

A. people living near the falls were used to the silence

B. the stop of the falls resulted from climate change

C. mysterious power may lie somewhere in the world

D. Niagara falls has never stopped since it came into being