单选题
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 intemational 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 shuffles.
______ Americans ever visited Mir during its lifetime.