From the first use of the rocket to carry satellites into space to the setting up of space
stations,human beings have been putting great effort into space research.And so far,we have
achieved many successes.But there are still numerous tasks in front of us and we should not
cease trying to progress.
     The international space station is an important step we should take in space exploration.
It is not only helpful but also essential.It provides a proper space environment for many
experiments that we have wanted to do for a long time.It is also a base for the observations
of the earth and the universe.It could also be an important base for later travels to the
moon and Mars.In a word,if we want to explore space more,the first thing we should do
is to set up a space station.
     As the space station costs a lot of money,it is hard for one country alone to establish
one.The USA seems to be the only country that has the ability to build a space station alone,
and it has tried to do so,but not very successful.So it aggregated many other countries to
work on it together.Though it is still extremely expensive,it is much cheaper than doing it
alone.It is really a job that needs everyone's effort and will benefit everyone.
     But even so,the funds needed are still a big problem.As for the USA,it seems that it has
too many things to spend its money on.Although it is the richest country in the world,it has
much debt every year.It has to make arrangements about its finance,and try to find a balance
in all these issues.

5．Which of the following aspects about building the international space station is NOT
 mentioned in the passage?