Directions:Complete the following passage by choosing the words in the box．Each

Directions：Complete the following passage by choosing the words in the box．Each word can only be used once．Note there is one word more than you need．

Using the power of the sun is nothing new．People have had solar-powered calculators and buildings with solar panels for decades．But plants are the real experts：they've been using 1 as an energy source for billions of years．

Cells in the green leaves of plants work 2 tiny factories to convert sunlight, carbon dioxide, and water into sugars and starches－stored energy that the plants can use, this conversion process is called photosynthesis(光合作用)．Unfortunately, 3 you're a plant, it's difficult and expensive to convert sun light into 4 energy．That's why scientists are taking a closer look at exactly how plants do it．

In a world with increasing energy needs, researchers are always looking for new ways to power everything from cars to computers 5 putting more stress on the environment．That's another reason why scientists are so interested in solar power－it doesn't pollute the air, water, or land．And since the sun lights and warms the entire planet, the ability to harness its energy could provide a clean energy 6 for everyone．

The main sources of energy that people use today are called fossil fuels, such as natural gas, oil, and coal．Unfortunately, the supply of fossil fuel is 7．Once we use all the coal and oil in the Earth, they're gone for good．The sun, on the other hand, is a 8 energy source．No matter how we tap it for energy, the sun will be around –at least for the next few billion years．

There's another problem with 9 fossil fuels－pollution．The ideal energy sources of the future will be“clean”：they won't produce carbon dioxide and other gases that pollute the environment as fossil fuels do．

试题答案

答案：sunlight;like;unless;storable;without;source;limited;renewable;burning