3．There was some trouble in space over the weekend．On Thursday May 9，flakes of frozen ammonia（氨） were seen drifting form the International Space Station（ISS）．The team on board immediately prepared for a spacewalk to look into the issue．Two days later，on Saturday，two astronauts stepped outside the ISS to investigate（调查） the leak．The chief suspect was an old ammonia pump．
Thomas Marshburn and Christopher Cassidy conducted the search，but did not discover any visible damage．"All the pipes look shiny clean，"Cassidy reported as he used a mirror to peer into the tight，deep openings．Even so，the astronauts removed the old pump and replaced it with a new one．
Ammonia is used on the ISS to cool the spacecraft's electronic equipment．NASA said this leak did not pose a safety threat to the six space station residents（常驻居民）．But problems with the cooling system could threaten experiments and equipment．
It is still not clear why exactly the leak erupted（ 喷发 ）．NASA speculates（ 推测 ） that a
microscopic piece of space matter struck the space station，leaving a tiny crack in the ammonia pump．Another possibility is that there was simply a leaky seal in the pipe．Either way，"there's nothing to lose by putting in a fresh pump and pressing ahead with additional detective work，"said Mission Control．
The ISS was launched into orbit in 1998．Since 2000，a crew of astronauts and scientists has continuously occupied it．While in orbit，the international team of astronauts could perform scientific research and data about conditions in the Milky Way and beyond．Many of their experiments focus on human's ability to live and work in space over long periods of time．
NASA astronauts Tom Marshburn and Chris Cassidy completed the May 11spacewalk in 5hours and 30minutes．While these astronauts have performed some amazing tasks，NASA has never before staged a spacewalk so quickly．Marshburn has been on the space station since December，and Cassidy is a new arrival to the ISS．While the leaky pump mystery continues to puzzle the ISS team，they hope further investigations will provide answers．"This type of event is what the years of training were for，"space station commander Chris Hadfield said on Friday．
32．From Paragraph 2we learn thatC．
A．it is impossible to peer into deep openings
B．it is very difficult to replace a pump
C．it was not easy to find the damage
D．some pipes have become too old
33．What is the main use for ammonia on the ISS？D
A．To prevent astronauts on the ISS from feeling too hot．
B．To prevent pumps on the ISS from getting old quickly．
C．To help astronauts stay safe when there is damage to the space station．
D．To prevent the spacecraft's electronic equipment from becoming too hot．
34．It is implied in Paragraph 4that Mission ControlA．
A．thinks changing the pump is necessary
B．wants to keep the cause of the problem secret
C．is sure that the space station has been struck
D．no longer wants to find out the cause of the problem
35．What does the last paragraph suggest about the recent spacewalk？C
A．It took too much time．
B．It was really dangerous．
C．It was quite satisfactory．
D．It wasn't amazing enough．
