A passage is given with 5 questions following it. Read the passage carefully and choose the best answer to each question out of the four alternatives.

The destructive process of mountaintop removal mining (MTR) has caused permanent damage to Appalachia. Although the law requires that mining companies restore the mountaintops after the mining has been completed, the 1.5 million acres of mountains that have already been removed cannot be regrown, re-built, or replaced. The companies do secure the rock formations to prevent erosion and landslides, but their efforts cannot recreate the once beautiful mountain landscape. Furthermore, while companies are usually vigilant about securing the rock formations, they seem less interested in restoring the native vegetation. MTR operations clear enormous tracts of forest; some experts estimate that over 2000 square miles of forests in the Appalachian region will have been razed by mining companies by 2012. Instead of replanting the native trees and shrubs that have been cleared,many companies opt to plant cheap, fast-growing, non-native plants, such as Lespedeza cuneata, which is officially classified by the USDA as an invasive weed.

Environmental hazards are not only created in preparing a mountaintop for mining, they also continue once the coal has been extracted. After the blast, the excess mountaintop—which miners refer to as “overburden”—is usually dumped into nearby valleys or streams. The overburden contains a variety of toxic substances, including explosive residue, silica, and coal dust. These substances are filled with sulphur, lead, mercury, and other chemicals. Over 700 miles of streams in Appalachia have been contaminated by this dumping. Although the mining companies have built structures known as “sludge dams” that are intended to contain the toxic runoff, these dams can burst or leak, sending thousands of gallons of toxic chemicals into municipal drinking water