The vast majority of us spend our entire lives pulled down by gravity.Then there are astronauts.
This small population of space travelers has given researchers a rare look at what happens to the human body when it’s able to spend large amounts of time outside the downward pull of the Earth.This week，a study on one of the largest groups of astronauts yet—34 participants—was published in The New England Journal of Medicine.
In the new study，a team of international radiologists(放射科医生)supported by NASA looked at MRIs of the brains of astronauts before and after their trips to space.The scientists found that upon returning to Earth，many of the astronauts’ brains had become repositioned inside their skulls，floating higher than before.In addition，the space between certain brain areas appeared to have shrunk(缩小)．The changes were more common in astronauts who took longer trips into space.
The team characterized astronaut trips as short(an average of less than 14 days)or long(an average of about 165 days)．Radiologists who didn’t know each astronaut’s duration(持续时间)in space compared MRIs from before and after their trips.
Of the 34 total astronauts involved in the study，18 took long trips to space—spending most of that time on the International Space Station—and of those，17 returned to Earth with smaller areas between the frontal lobe(脑前额叶) and parietal lobe(顶叶)．The same area of the brain also shrank for three of the 16 astronauts who took shorter trips with the US Space Shuttle Program.The researchers also found that 12 of the ISS astronauts and six of the spaceshuttle astronauts returned home with their brains sitting slightly higher in their skulls than before.
It’s not clear what，if anything，these brain changes mean for the health of space travelers.In general，it appears the human body tolerates space travel fairly well：the time astronauts have spent in zerogravity environments so far doesn’t seem to have had any strong or longlasting effects.
【解题导语】 本文是一篇说明文。放射科医生研究发现，宇航员从太空返回地球后，他们的大脑在颅内的位置比去太空旅行前高。
1．What is the finding of the study?
A．Astronauts have great brain power.
B．Astronauts’ duration in space is updated.
C．Astronauts’ skulls expand after space trips.
D．Astronauts return to Earth with raised brains.
D 解析：细节理解题。由第三段中的The scientists found that upon returning to Earth，many of the astronauts’ brains had become repositioned inside their skulls，floating higher than before.可知，科学家发现，宇航员在返回地球后，他们的大脑在头颅内的位置改变了，悬浮在比以前更高的位置。
2．How did the scientists draw the conclusion?
A．By analyzing astronauts’ symptoms.
B．By comparing each astronaut’s MRIs.
C．By monitoring astronauts’ brain activities.
D．By observing countless astronauts’ behaviors.
B 解析：细节理解题。由第四段中的Radiologists who didn’t know each astronaut’s duration(持续时间) in space compared MRIs from before and after their trips.可知，放射科医生通过比较每位宇航员太空旅行前后的脑部核磁共振成像，得出研究结论。
3．What does the author say about the changes inside astronauts’ skulls?
A．They are totally harmless.
B．Their effects are hard to assess.
C．Their occurrence is unavoidable.
D．They will heavily influence astronauts.
B 解析：推理判断题。由最后一段中的It’s not clear what，if anything，these brain changes mean for the health of space travelers.可知，宇航员在经历太空旅行后大脑的这种变化是否意味着对他们的健康有影响，这一问题目前还没有明确的解释。
4．What is the best title for the text?
A．Effects of Zero Gravity
B．Valuable Experiences of Space Travel
C．Space Travel Changes Astronauts’ Brains
D．Flying Long Hours Increases Health Risks
C 解析：标题归纳题。通读全文可知，本文主要讲述了放射科医生经过研究发现，宇航员从太空返回地球后，他们的大脑在头颅内的位置改变了，悬浮在比以前更高的位置，C项作标题最能概括文章主旨。
