Starting in l972，the National Park Service established a policy for forest fires calle Natural Burn．It was acknowledged that some forest fires，such as those caused by lightning were necessary for forests to maintain balanced ecosystems，so the fire should be allowed to burn．However, a big fire in Yellowstone National Park in l988 caused this policy to be abandoned since the fire was initially allowed to burn yet soon out of control．As a result，the fire of l988 destroyed much of Yellowstone，which is America’s oldest and most beloved national park．Massive areas of plants were destroyed，and large empty spaces and acres of burned and blackened trees greeted visitors．The rivers and streams were choked with ash，and the ecosystem of the park was changed beyond repair.
In addition，great numbers of animals were killed by the fires that bumed out of control. The fires were driven by high winds，moving as many as ten miles a day．Many small animals died in the flames．The fires’ rapid advances gave the wildlife little chance to escape. Even today，few of these small forest animals have returned to live in the park. In the years immediately following the fires，the numbers of visitors declined rapidly．No one was interested in seeing a blackened and treeless park on vacation．Yellowstone had previously been famous for its amazing views and unique geological formations such as the geyser Old Faithful. But now its reputation as America's wonder is damaged permanently.
Natural Burn was adopted because some forest fires were        

A．hard to put out

B．started by lightning

C．good for the balance of nature

D．approved by National Park Service

The big fire in Yellowstone in 1988         ．

A．became out of control at first

B．destroyed the park completely

C．was allowed to burn continuously

D．brought the natural burn policy to an end

Why were so many animals killed in the big fire?

A．Because winds were blown from high places．

B．Because the animals moved only ten miles a day．

C．Because the animals lived in lower places．

D．Because strong winds contributed to the fire a lot．

Yellowstone was famous for its        ．

A．rare animals

B．unique plants

C．beautiful scenery

D．little streams

The text probably comes from   ．

A．a science fiction	B．a news report
C．a commercial ad	D．a geography magazine