輕松學英語每日一練(294)
閱讀下面短文，在空白處填入1個适當單詞或括号内單詞的正确形式。
Burning coal for energy adds planet-warming carbon dioxide (二氧化碳) to Earth's atmosphere. As the planet heats up, experts warns that ___1___ (simple) cutting greenhouse gas emissions (排放) will not be enough to avoid global warning. Carbon dioxide must be ___2___ (remove) from the atmosphere.
Existing experimental machines that pull carbon dioxide directly from the air ___3___ (be) too expensive to be widely used. But a new ___4___ (effect) technology to remove carbon dioxide already exists. It is not expensive and easy. It is forests. ___5___ (plant) trees and watching forests are effective ways to clean the air.
Forests used to cover large areas of the Appalachian Mountains in the ___6___ (east) United States. In the state West Virginia, coal mining let the land there bare, without trees. Over the years, coal mining ___7___ cutting forests took over 90 percent of the red spruce (紅杉) forests.
Chris Barton works for the University of Kentucky. He started a group called Green Forest Work, aiming to put trees back on the roughly 400,000 hectares (公頃) of land.
However, Barton explains the land has problems. "___8___ you planted on these places, they just didn't grow. The ground was too hard. Water didn't infiltrate(滲透). The trees can't root. Oxygen can't circulate in those environments." Using heavy ___9___ (equip), workers tear the ground. In this way, the trees put down roots.
Barton says ___10___ everyone believes the solution is a good idea. "We've had a lot of doubtful look at us twice from people. But after we do it, there is no question that it was the right thing to do." And it has worked. Forests are coming back to the grounds.
