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  3. Forest Service officials say there are four major threats to forests and wild lands in America. The first is the threat of fire

Forest Service officials say there are four major threats to forests and wild lands in America. The first is the threat of fire

admin2009-04-23  57
问题     Forest Service officials say there are four major threats to forests and wild lands in America. The first is the threat of fire and fuel. This year, fires have 【S1】______ more than three million hectares of land. That is 【S2】______ two times as much as the ten-year average. Fuel is dead plant material and small plants that 【S3】______ under tall trees. The Forest Service estimates that up to one-fourth of the forests it 【S4】______ have dangerous levels of fuel.
    Another threat to forests is from invasive species. These are non-native plants and animals that push out 【S5】______ kinds. They can cause a lot of economic damage. Some 【S6】______ are insects. Some are diseases. Others are plants.
    The 【S7】______ says another threat to the health of wild lands is the loss of open space. It says over one hectare of forest or grassland is lost to development every minute. Development also leads to the 【S8】______ of large natural areas into smaller ones. Many animals need wide open spaces. Also, building near wild lands increases the risk to homes from forest fires.
    The fourth threat to public lands is what the Forest Service calls 【S9】______ recreation. People can hunt, fish and camp in many national forests. But careless 【S10】______ of motor vehicles and other actions can be destructive.

               Word Bank:
A. expansion               I. native
B. burned                  J. unmanaged
C. invaders                K. virtually
D. monitors                L. use
E. agency                  M. almost
F. grow                    N. division
G. supervises              O. lit
H. institute
选项
答案B
解析 根据句子结构此处应为动词的过去分词，符合的有B和O；但根据文意可知这里说的是森林大火每年要烧掉三百万公顷土地。lit“点燃”，原形为light。所以应选B。
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