In the books The Three-Body Problem，Trisolarans （三体人），a type of alien，can dehydrate （脱水） their bodies.They can then ride out terrible environments and come back to life again hundreds of years later.Is it possible that humans could be like that as well？
   Scientists have now found some clues by studying water bears which can live without water for decades，according to University of Tokyo biologist Takekazu Kunieda.
   When water bears find themselves somewhere without water，they go into a form called a tun.In this form，there are no signs of life，and they can survive pretty much anything.Deep freezing，volcanic fire，the dark space ...these tiny water bears just sleep it off and wake up once they are safe again.
   But how do these little eight-legged water bears live without water？Scientists may be onto the answer now.
   "It's thought that as water leaves a cell，some kind of protein must help the cell keep its strength to avoid breaking apart，" said Kunieda.Now scientists have found proteins special to water bears.The proteins protect their cells against dehydration.
   Scientists also put those proteins into human cells.They found these proteins can strengthen the human cell so that it won't shrink when losing water.With experiments using human cells showing successful results，Trisolarans might one day come to be a reality.

（1）What can Trisolarans do？

D

D

A．They can protect themselves from dehydration.
B．They can live in water for hundreds of years.
C．They can help other dead things come back to life.
D．They can dehydrate themselves and live in bad environments.
（2）What does a water bear do when there is no water？

C

C

A．It becomes a tun.
B．It goes to live near volcanic fire.
C．It finds a dark space to sleep in.
D．It gives up living.
（3）What is the key for water bears to live without water？

C

C

A．Their special cells.
B．Their way of dehydrating.
C．A kind of protein in their bodies.
D．The strength of their body.
（4）What is the passage mainly about？

C

C

A．How humans can live underwater.
B．What water bears can do for humans.
C．A scientific finding on water bears.
D．The story of The Three-Body Problem.