B

   Waves are beautiful to look at, but they can destroy ships at sea, as well as house and buildings near the shore. 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 depends on 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 giant, powerful waves.

   A rule says 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 per hour, most waves will be about twelve meters. Of course, some waves may combine to form giant waves that are much higher. In 1933 the United States Navy(海军) reported the largest measured wave in history. It rose in the Pacific Ocean to a height of thirty–four meters

   1.One can guess the height of a wave by knowing _____________.

   A.how fast the wind is blowing

   B.how long the wind blows

   C.how large the body of water is 

   D.how the wave is built up

   2.The largest measured wave in history was in ___________.

   A.the Indian Ocean

   B.the Atlantic Ocean

   C.the Pacific Ocean

   D.the Mediterranean Sea

   3.When the wind is blowing at 80 kilometres per hour, the height of most waves will be _______.

   A.about one meter

   B.about eight meters

   C.about eighty meters

   D.about ten meters

   4.Air rises when __________.

   A.the wind is blowing

   B.the body of water is large

   C.this is a powerful earth

   D.the sun heats the earth

   5.The best title for this selection is ____________.

   A.What causes Waves?

   B.The Largest Waves in history

   C.Beautiful Waves

   D.Waves in Pacific Ocean

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