What will astronauts （字航员） eat when a space trip takes years？

   "Lots of fresh vegetables，" says Dr． Janet Williams， whose team have spent the last 10 years learning how to grow plants in a space station． And it's a good thing that she has already started her work， because space gardening can be really hard．

   As usual， astronaut George White looked into the closed plant room． He had planted Dr． Williams's quick﹣growing seedlings in it， but none of the stems were showing． He opened the room to check and found the problem． The stems weren't growing upward and the roots weren't growing downward． On Earth， gravity （重力） helps a plant's stems and roots to find"up" and"down"． However， in the space station，there was almost no gravity．

   Dr．Williams suggested a solution： give the plants more light，as plants also use sunlight to find their way． And it worked． When the plants had more light， the stems turned up and the roots went down．

   Now Dr．Williams was free to worry about the next problem： Would her baby plants live to flower？ Can we grow food on a space journey？

   Many plants died in the space station． Dr．Williamns thought she knew why： the space plants were hungry for air． Plants live by taking up CO ₂from the air． Since a plant uses itup in the air around， the plant needs moving air to bring more CO ₂close to its surface． On Earth， the air is always moving． Gravity pulls down cold air， and warm air rises． And with these air movements，plants get enough CO ₂．

   Many earier experiments with plants in space hard used closed rooms． Dr Williams tried a new greenhouse that had a fan to keep the air move． The plants loved it． They flowered and even produced more seeds． Using Dr． Williams's method， astronaut George completed the first seed﹣to﹣seed experiment in space， and moved one plant closer to a garden in space．

   "And this，" says Dr． Williams，"is good news for long﹣term space travel．"

（1）Why have Dr． Williams's team tried to grow plants in space？ 　　

A．	To produce fresh air for astronauts．
B．	To help astronauts relax themselves．
C．	To provide food for long space journeys．
D．	To make the space garden more beautiful．

（2）How did light help solve the problem mentioned in Paragraph 3？ 　　

A．	It caused the gravity to change．
B．	It encouraged the plants to grow faster．
C．	It helped the plants to grow in the right direction．
D．	It showed the astronauts where to plant vegetables．

（3）Why did many plants die in the space station？ 　　

A．	The light was too strong．
B．	There was too much CO 2．
C．	There was not enough room to grow．
D．	The air condition was not good enough．

（4）The underlined word "it" in Paragraph 7 refers to 　　．

A．	the moving air
B．	the closed room
C．	the space journey
D．	the space garden

（5）What can we learn about Dr． Williams's team from the passage？ 　　

A．	They mainly live on fresh vegetables．
B．	They have successfully built a space garden．
C．	They invented a special fan for their greenhouse．
D．	They have worked on space gardening for many years．