A、By recycling all the water. B、By using very little. C、By transporting plenty from Earth. D、By controlling the humidity on boar

WOMAN: Welcome to this week’s edition of "Frontiers of Science". The International Space Station—the ISS—is a floating laboratory, 350 km above the earth. But what exactly is it and who is behind it? To answer our questions, we are pleased to welcome Dr Karl Richter who is a specialist in this field.
MAN: Delighted robe here.
WOMAN: Dr. Richter, who is behind this venture?
MAN: The ISS is a joint venture between America, Russia, Japan, Canada, Brazil and the 15 nations of the Europe Space Agency.
WOMAN: So that’s... 18, 19, 20 countries in all.
MAN: Yes, it is. Actually, it is the largest and most complex international scientific project in history.
WOMAN: Wow! And can you tell us how much it’s going to cost?
MAN: Well, despite the fact that it was estimated to cost $120 billion, it has already gone 8 billion over budget, so now we’re looking at 128 billion.
WOMAN: And what size will it be?
MAN: Well, it will measure 108 meters across by 88 meters long with almost half a hectare of solar panels powering six scientific labs.
WOMAN: Ok. So it’s no small venture, is it? Now, I must ask you this question. What do they do about water on board?
MAN: Good-question! Well, nothing goes to waste, but hygiene in space is a complex affair. Because of the impracticality of transporting large amounts of liquid into space, they’ve come up with some ingenious solutions. For instance, everything on board, including the laboratory rats, loses water when it exhales or sweats. The humidity goes through condensation process before being returned to the water supply.
WOMAN: I see.
MAN: If they didn’t reuse the water, the station would, need about 20,000 kg of water a year, which just couldn’t be done.
WOMAN: Going back to the laboratories. What’s happening there?
MAN: Well, we have teams of astronaut-scientists working in the labs and research will include, for example, tissue culture, studying life in low gravity, the nature of space, observations of the earth from space with a view to improving our maps, and the development of new commercial products;
WOMAN: I can’t imagine what it must be like to live without gravity. Can you tell us about the life of astronauts there?
MAN: Sure...
Questions:
27.How many nations are involved in the ISS?
28.How much should the ISS have cost to build, according to their original estimate?
29.How is the water supply maintained on board?
30.What area of research was not mentioned by the man?