Not many people have seen (看见) icebergs. Sailors (船员) sometimes see them but they (1)   

     to keep away from them. We call the top and bottom (底部) of the world the North and South Poles (极点). Here there is ice over the sea and the (2)        . The ice is often thousands of meters thick(厚). The ice often moves slowly down (3)           the sea. Then big pieces of ice break off and float (漂浮) on the sea . We (4)         these big pieces Office "icebergs".

    Most of an iceberg is under the water. Ice is only a little (5)        than water. The top of an iceberg may not be near (6)         a ship, (7)       the ship hits the iceberg below the water. Then the ship (8)        . Sometimes the water becomes (9)      . The bottom of the iceberg becomes smaller and smaller. Then it turns right over. Sometimes it hits a ship. Icebergs are often very beautiful but they are also (10)           .