阅读理解。
Contrary to people's previous knowledge, it's food shortage not dietary preference that motivates birds to migrate thousands of miles back and forth between breeding and non­breeding areas each year, a new research shows.
“It's not whether you eat insects，fruits or candy bars or where you eat them that counts，but how reliable that day­to­day food source is，” said the study leader W．Alice Boyle of the University of Arizona.
To figure out the underlying pressure that drives some birds to leave home for the season，Boyle examined 379 related species of New World flycatchers(捕蝇鸟) and compared their sizes，food types, habitats, migratory behaviors and whether or not they fed in flocks.
To compare the birds，the researchers constructed a “supertree”   showing the exact evolutionary relationships among different species.
A computer analysis then determined whether a particular species was migratory because it ran in the “family” or whether something in the bird's environment was forcing it to leave each season.Boyle and her colleagues found that food shortage was the number one issue that predicted a species' migratory behavior. “Food availability is the underlying pressure, not diet and habitat，” Boyle said.
An alternative strategy that the birds use to handle food shortage is to hunt in flocks, since a group is more likely to find a new source of food than an individual.
“If you suffer from food shortage, you have two options，” Boyle said.“You can either hunt with other birds or you can migrate.”
1. Birds were thought to migrate in order to ________.

A．seek their favorite food in a new place

B．avoid being constantly hunted

C．breed more young in a new place

D．adjust themselves to the changes of weather

2. What is Paragraphs 3 and 4 mainly about?

A．The aim of the research.

B．The basis of the research.

C．The process of the research.

D．The findings of the research.

3. The passage implies that ________.

A．the birds' food sources are getting rare in the world

B．the living surroundings are severe for birds

C．birds search for food separately

D．birds can survive only by hunting in flocks

4. For what purpose does the author write the text?

A．Educating readers.

B．Informing readers.

C．Drawing people's attention.

D．Condemning the bad environment.

While astronauts in space get to do many exciting things，they miss out on ordinary things that we all take for granted—being able to walk on firm ground，hanging out with family and digging into a slice of hot steaming pizza． Though not much can be done about the first two things，there may soon be a solution to the third one，thanks to this cool 3-D pizza printer！
About a year ago，NASA offered $125 ,000 to Anjan Contractor， a 3-D technology expert，to build a device（设备）that would allow astronauts to make pizza on demand． The mechanical engineer promised that his invention would produce pies in large quantities that looked， tasted and even smelled like pizza made in common ovens．
Late last year， the engineer presented a video of his first prototype（原型）that begins by creating a single slice of dough（面团）that is cooked and printed at the same time．Then comes the tomato “sauce” — a mix of tomato powder，oil and water and finally，a protein slice that resembles cheese．While the video doesn’t show the baking process，the inventor says that once the pizza is printed，it can be ready to be consumed in 7 seconds．
While the pie in the video looks delicious enough to attract any pizza lover，Anjan Contractor is far from ready for astronauts．That’s because he still has to find a solution to make the food container in the printer last for 30 years．Though that may sound unrealistic，actually it is not．
Anjan Contractor believes that the only way that is possible is that the water is removed from all the ingredients（配料）and then they are reduced to the powder form．This，as you can imagine，will not be so easy．But，while the printer may not be ready for space，it certainly looks ready enough for people on earth．Hopefully，NASA and Contractor will consider selling it to those not fortunate enough to go to Mars！
5. Why does the author mention the things that astronauts in space cannot do？

A．To ask us not to take common things for granted．

B．To show they live a difficult life there．

C．To show their life is boring in space．

D．To introduce the topic of the text．

6. NASA offered $ 125，000 to Anjan Contractor mainly to _______．

A．create some new type of 3-D printer

B．attract more companies to work for NASA

C．help astronauts in space enjoy fresh pizza one day

D．produce pizza in large quantities to earn great profits

7. The biggest challenge that Anjan Contractor is faced with now is probably that _______．

A．he has no money left to go on with his research

B．the pizza doesn’t seem appetizing to pizza lovers

C．he has no way to make pizza that can last for thirty years

D．he cannot make the food container last for decades

8. What’s the best title of the passage？

A．NASA is trying its best to help astronauts eat better

B．Astronauts may soon be able to enjoy steaming hot pizza

C．NASA is working on making pizza for common people

D．A 3-D pizza printer has been used to make pizza

阅读理解。

Being an astronaut sounds cool, doesn't it? In space, they get to do some pretty amazing things, like floating in zero gravity.

However, there are also plenty of things that astronauts can't do because of their weightless environment, and that's very sad. What's worse, they can't even let their sadness show—because it's impossible to cry in zero gravity.

Of course, astronauts can still produce tears. But crying is much more difficult in space，reported The Atlantic in January. Without gravity, tears don't flow downward out of the eyes like they do here on Earth. This means that when you cry in space, your tears have nowhere to go—they just stick to your eyes.

In May 2011, astronaut Andrew Feustel experienced this during one of his spacewalks. “Tears,” he said, “don't fall off your eye... They just kind of stay there.”

Besides making your vision unclear, this can also cause physical pain. Back on Earth, tears are supposed to bring comfort to the eyes. But that's not the case in space. The space environment dries out astronauts' eyes, and when tears suddenly wet the eyes, it can cause pain rather than comfort. “My right eye is painful like crazy.” Feustel told his teammate during the walk.

Since gravity doesn't work in space, astronauts need some extra help to get rid of the tears. Feustel chose to rub his eyes against his helmet to wipe the tears away. Another choice is to just wait—“When the tears get big enough they simply break free of the eye and float around,” astronaut Ron Parise told The Atlantic.

There are lots of small things—things like crying—that we are so used to on Earth. We usually take them for granted, until they become a problem in a totally different environment, like space. There, astronauts can't talk to each other directly. They also can't eat or drink in normal ways. They can't even burp (打嗝), because there is no gravity to hold the food down in their stomach. If they do burp, they just end up throwing up (呕吐) everything in their stomach，according to the UK National Space Center.

Thus, perhaps it's only space explorers who can honestly say: “Gravity, you're the best.”

9. What can we conclude from Paragraphs 2 and 3?

A．Astronauts are unable to feel sad in space.

B．Astronauts produce fewer tears in space.

C．Tears produced in space flow down more slowly.

D．Tears produced in space don't flow downward.

10. What effect do tears have on astronauts?

A．They cause physical pain.

B．They bring comfort to them.

C．They make their vision clearer.

D．They float around and cause trouble.

11. What can the astronaut do to get rid of the tears?

A．Rub his eyes against his helmet to let the tears float forward.

B．Rub his eyes by hand to let the tears float around.

C．Get the tears big enough to fall off of his eyes.

D．Get the tears big enough to break away from his eyes.

12. What's the last but one paragraph mainly about?

A．Suggestions on how astronauts can stay comfortable in space.

B．Other basic things that are difficult to do in space.

C．Why burping is impossible in space.

D．Things that humans can't do without gravity.