Waves are beautiful to look at, but they can destroy ships at sea, as well as houses 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 wavessintosbigger 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 miters. Of course, some waves may combine to form giant waves that are much higher. In 1933 the United States Navy reported the largest measured wave in history. It rose in the Pacific Ocean to a height of thirty-four meters.

　　1.______ cause(s) waves.

　　A. The sun

　　B. The earth

　　C. The air

　　D. The winds

　　2.The size of a wave depends on ________ factors.

　　A. one

　　B. three

　　C. two

　　D. four

　　3.Big waves will build up_____.

　　A. near the shore

　　B. over the surface of water

　　C .in a small bay

　　D. at sea

　　4.As a rule, the height of a wave is _____ one-tenth of the wave’s speed.

　　A. no more than

　　B. more than

　　C. no less than

　　D. less than

　　注释：1. giant n.巨人,大力士,巨大的动物或植物,伟人,天才

　　adj.庞大的,巨大的

　　Shakespeare is a giant among writers.

　　莎士比亚是一位文坛巨匠。

　　2. no more than adv.只是

　　more than enough太多,够多,十二分

　　less than小于,决不

　　no less than conj.正如

　　答案：1:D 2:B 3:D 4:A