Is there an energy problem? Some people (1)…………. so. Using oil is bad because it makes (2)…………. air. In addition, there might not be much (3)…………. in 30 years. One possible answer is energy (4)……………… wind. How does wind power work? Special machines change wind into electricity. They are called wind (5)………….. .These big, heavy machines can weigh 300 tones and stand (6)…100… meters. Sometimes you can see a large group of turbines in the (7)…countryside….. or near the sea. That is called wind farm. Many wind turbines have three long sticks (8) …………….blades. When the wind moves, the blades turn. When blades turn, they (9)……………. a special stick called a shaft. The shaft turns generators which make electricity. One large turbine can (10)…………enough power for about 300 homes for a year. That number depends on the (11)………….. of the turbine and amount of wind. Not everyone thinks wind turbines (12) …………….good. Turbines make a lot of sound and kill a lot of birds. They also (13)……cost…….. a lot of money. Often, people in a city with a wind farm pay more (14)…………….electricity, not less. There is one serious problem. Wind power cannot (15)…………….other energy, like coal or oil. That is because wind power does not (16)…………… work. When the wind stops, there is no electricity. That means a city needs another (17)…………… to make power. Cities that buy wind power have to purchase another (18)………….. of energy.Wind power seems like a (19)……good……. idea, but today, the cost is high and its benefits are (20)………limited…………...