The longest river in the world is the Nile． It is 4，160 miles long． But the Nile is not the mightiest （浩荡的） river． The Amazon is．The Amazon is also the second longest river in the world．It is 3，900 miles long． How long is that？ It is longer than a road going from New York City to San Francisco．

    The Amazon is the mightiest for this reason． It has the greatest amount of water． More water runs out to sea than from the Nile． Mississippi， and Yangtze rivers combined． That's a lot of fresh water! The force of its current （水流） is great too． The current can be seen 200 miles out in the sea． There's a story to show the Amazon's amazing current． A ship sailed （航行） far away from Brazil． It ran out of drinking water． Another ship passed by． The first ship asked for water． Someone on the second ship said． "Just put your buckets （桶） into the sea．"

    Here are a few more facts． At its mouth， the Amazon is 90 miles wide．Even up the river，you can't see the opposite bank． The river is also very deep（from 22 to 76 meters）．During rainy season，the river rises about 16 meters more． Big ocean ships can sail about 1，800 miles upstream （向上游）．Smaller ships can sail 1，000 miles farther．

    What's the most bloodthirsty fish in the world？ No． It's not the shark． It's the Amazon's piranha． It is only about 10 cm to 20 cm long． It has sharp teeth． Thousands travel in a group． No animal can swim across the river．A 1，000﹣pound horse would be just bones （骨头） in three minutes． Are you planning a trip to the Amazon？ Here's a piece of advice． Leave your swimsuit at home!

根据短文内容，选择最佳答案．

（1）After reading this passage it seems clear that　　．

A． people do not drink the Amazon's water

B． it would not be good to visit the Amazon during rainy season

C． sailing on the Amazon requires：knowledge of its current

（2）The writer helps you understand how long the Amazon is by　　．

A．telling how long the Nile is

B． comparing it to a distance（距离）on land

C． comparing it with the Yangtze River

（3）In Paragraph Four， the word "sharp" means"　　"in Chinese．

A．锋利的

B．急剧的

C．强烈的

（4）The passage mainly tells us　　．

A． piranha in the Amazon

B． traveling in the Amazon

C． interesting facts about the Amazon