Waves（波浪） are beautiful to look at，but huge waves are greatly harmful to ships at sea，as well as houses and buildings near the seaside．What causes waves？ Most waves are caused by winds blowing over the surface of the water．The sun heats the earth，causing the air to rise and the winds to blow．The winds blow across the sea，pushing little waves into bigger and bigger ones．

The size of a wave is decided by how strong the wind is，how long it blows，and how large the body of water is．In a small bay，big waves will never build up．But at sea the wind can build up big，powerful waves．

It is believed that the height of a wave （in meters）will usually be no more than one tenth of the wind's speed （in kilometers）．In other words，when the wind is blowing at 120 kilometers an hour，most waves will be 12 meters high or less．Of course，some waves may come together to form big waves that are much higher．

（1）What are huge waves greatly harmful to？ 　　

A．	Ships at sea．
B．	Houses in the city．
C．	The living things in the sea．
D．	Buildings in the town．

（2）What causes waves？ 　　

A．	Ships' pushing the water．
B．	The sun's heating the earth．
C．	Sharks' running after each other．
D．	Winds' blowing over the surface of the water．

（3）According to the passage，which statement is NOT true about the size of a wave？ 　　

A．	It's decided by how strong the wind is．
B．	It's decided by how long the wind blows．
C．	It's decided by how far the wind blows．
D．	It's decided by how large the body of water is．

（4）What does the underlinedword "bay" mean in Chinese？ 　　

A．	"海湾"．
B．	"海滩"．
C．	"河流"．
D．	"湖畔"．

（5）When the wind is blowing at 168 kilometers an hour，how high will most waves be？ 　　

A．	12 meters．
B．	16 meters．
C．	168 meters．
D．	240 meters．

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