单选题：The Mir Space Station The Russian Mir Space Station，which ca

The Mir Space Station
The Russian Mir Space Station，which came down in 2001 at last after 15 years of pioneering the concept of long—term human space flight，is remembered for its accomplishments in the human space flight history．It can be credited with many firsts in space．
During Mir’s lifetime，Russia spent about US$4．2 billion to build and maintain the station．
The Soviet Union launched Mir，which was designed to last from three to five years，on February 20，1986，and housed 104 astronauts over 12 years and seven months，most of whom were not Russian．In fact，it became the first international space station by playing host to 62 people from 11 countries．From 1995 through 1998，seven astronauts from the United States took turns living on Mir for up to six months each．They were among the 37 Americans who visited the station during nine stopovers by space shuttles．
The more than 400 million the United States provided Russian for the visits not only kept Mir operating，but also gave the Americans and their partners in the international station project valuable experience in long—term flight and multinational operations．
A debate continues over Mir’s contributions to science．During its existence，Mir was the laboratory for 23，000 experiments and carried scientific equipment，estimated to be worth $80 million，from many nations．Experiments on Mir are credited with a range of findings，from the first solid measurement of the ration of heavy helium atoms in space to how to grow wheat in space． But for those favoring human space exploration，Mir showed that people could live and work in space long enough for a trip to Mars．The longest single stay in space is the 437．7 days that Russian astronaut Valery Polyakov spent on Mir from 1994 to 1995．And Sergie Avdeyev accumulated 747．6 days in space in three trips to the space station．The longest American stay was that of Shannon Lucid，who spent 188 days aboard Mir in 1996．
Despite the many firsts Mir accomplished，1997 was a bad year out of 15 for Mir．In 1997，an oxygen generator caught fire．Later，the main computer system broke down，causing the station to drift several times and there were power failures．
Most of these problems were repaired，with American help and suppliers，but Mir’s reputation as a space station was ruined．
Mir’s setbacks are nothing，thongh，when we compare them with its accomplishments．Mir was a tremendous success，which will be remembered as a milestone in space exploration and the space station that showed long—term human habitation in space was possible：But it’s time to move on to the next generation．The International Space Station being built will be better，but it owes a great debt to Mir．
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