The space shuttle Discovery has had a long and busy career. For 27 years, it has worked for NASA, carrying astronauts to space and back on 39 missions. On March 9, 2011, after returning from its final voyage, the world’s most traveled spaceship was retired.
A crowd of shuttle workers, reporters and schoolchildren waited to greet Discovery at Kennedy Space Center in Cape Canaveral, Florida. Three minutes before noon, they watched as the shuttle appeared in the sky and made one last touchdown. “For the final time: wheels stop,” Discovery’s commander Steven Lindsey said when the shuttle rolled to a stop.
Discovery’s final trip was to the International Space Station (ISS), a giant space lab in the sky. Discovery’s crew took care of the last U.S. construction project at ISS. They delivered 10 tons of supplies for the ISS. The six-person crew also dropped off an unusual companion for ISS’s researchers: a human-like robot named Robonaut 2. Astronauts will assemble（组装）R2 at the ISS over several months.
Now, NASA is winding down its shuttle programme. NASA is to begin work on new spaceships that can travel longer distances. Discovery’s retirement is the first of three. Endeavor, another shuttle, is scheduled to make its final voyage soon. And Atlantis’s last trip is planned for the end of June.
Museums across the country have requested the retired shuttles. The Smithsonian’s Air and Space Museum, in Washington, D.C., was the lucky recipient（接收者）of Discovery. The museum’s collection contains hundreds of NASA artifacts.
Where will the other shuttles go? You’ll have to wait to find out. NASA will announce its decision on April 12, the 30^th anniversary of the first space shuttle launching. Stay tuned!
As part of the final mission, Discovery’s crew___________.

A．carried researches to space

B．assembled the Robonaut 2 at the ISS

C．brought supplies to the ISS

D．went on a spacewalk

The underlined phrase “winding down” in Paragraph 4 probably means _________.

A．improving

B．ending

C．changing

D．testing

What can we infer from the text?

A．Discovery completed 39 missions during its two decades of space travel.

B．The ISS is a big project and six researchers live on the station.

C．American space exploration will focus on longer missions.

D．The shuttles Endeavor and Atlantis will make their last missions next month.

According to the text, we can learn about ___________.

A．people’s opinions of Discovery’s retirement

B．the government’s concern about the shuttles’ future

C．the shuttles’ final homes after retirement

D．museums’ great interest in the retired shuttles