7．
阅读理解
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 the 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 metres) will usually be no more than
one-tenth of the wind's speed (in kilometres). 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 came together to form big waves that are much higher.
