Visiting a National Park can be relaxing, inspiring and rejuvenating, but it can also be disturbing. As you drive into Rocky Mountain National Park, and you will see starving elk, damaged meadows and dying forests. Our parks are growing old because we have mistakenly protected them from natural processes, such as fire, predation, and insects. We believed that we were saving these remnants of wild America, but actually we have "protected" them to death. If we want to save our National Parks, the National Park Service must change its management priorities to-prevent over population of animals and to restore natural process in the forest in order to prevent their stagnation and "death" by old age. We must act soon: our parks are dying of old age because we have altered the forces in nature that keep them young and strong.
By tracing the history of our National Parks, we can understand the problem and see why we need active management. In the early part of the 20th century, settlers exploited wildlife heavily, resulting in near-extinction of many species. Therefore, several National Parks were established by Congress primarily to save endangered animals. However, stricter wildlife protection laws and improved wildlife management techniques resulted in greater populations of animals overcrowding in areas of high concentration, such as the Yellowstone elk herds. Complicating the problem, the National Park Service in the early part of the 20th century adopted a policy of aggressive predator elimination, thus reducing natural wildlife population control. Subsequently, elk and deer populations exploded in many National Parks, resulting in severe damage to native vegetation. Vigorous forest fire and insect suppression in the National Parks throughout the 20th century further altered the natural environment by allowing forests to over-mature, without natural thinning processes. Park managers thought that they were protecting the land, but actually they were removing important controls from the forest ecosystems.
Clearly, we must act immediately if we want to pass down to our children and grandchildren the green legacy of our National Parks; we must step in and restore the natural processes which we have altered through our well-intentioned, but misguided, policies in the past.
According to the article, strict wildlife protection laws and improved wildlife management techniques ______.

A. caused the near extinction of the endangered animals.
B. intervened the natural process.
C. made the visit of National Parks relaxing, and inspiring and rejuvenating.
D. saved the elks in the Rocky Mountain Park from starvation.