Have you ever looked up to the sky at night，gazed at the stars or planets and wondered if they might be able to support intelligent life？This stirs up the question？Is there extra-terrestrial life in the universe？Primitive （遠古的） cavemen 30，000 years ago might have been the earliest to wonder this time worn question，since pictures and drawings of aliens （外星人）have been found in their caves．
Today，this question is still considered by many people，especially astronomers and scientists．Astronomers have been paying close attention to the adaptability of some creatures．For example，creatures，like the anglerfish，have adapted to survive m total darkness and the incredible water pressure which is 100 thousand times the atmospheric pressure at sea level．Some creatures live on the ocean floor to get their energy，without any sunlight．Some microorganisms can survive in temperatures from-400 to 400 degree Fahrenheit，and require very little water to live．And certain bacteria can tolerate 200 degree Fahrenheit．Planets，such as Jupiter，have dense atmospheric pressure．Another planet that might sustain life is Mars which is a cold world without water．
Every day astronomers are listening for any kind of noise that could indicate another world trying to contact us．Another question remains：Could we communicate through words or by other means？Some astronomers have high hopes that we could．They are looking at how some animals，like the gorilla，are being taught to speak to people．Humans are now able to communicate with dolphins，elephants，domesticated animals，etc．These astronomers think the aliens must be much smarter than animals．
It may seem easy to accept the idea that alien life does not exist because there has not been any hard evidence to prove it．It means that there's a good chance that we're alone in the universe．For now，those who believe in the existence of alien life can just hope and study the question．As an 18th century writer once said，"It is absurd to think that in a field sown with millet （小米），only one grain will grow："

（1）The writer mentions cavemen to show that

D

D

．
A．a(chǎn)ncient people admired the aliens
B．a(chǎn)lien life visited Earth in ancient times
C．the search for aliens started from ancient times
D．even ancient people wondered about the existence of aliens
（2）What can we learn from Paragraph 2？

C

C

A．The species on earth are diverse．
B．Some animals live a difficult life．
C．Creatures may survive on other planets．
D．Some creatures can adapt to different environments．
（3）What is the 18th century writer's attitude towards the existence of alien life？

A

A

A．Positive．
B．Unknown．
C．Negative．
D．Unsure．
（4）What is the main purpose of the passage？

A

A

A．To argue about the possibility of alien life．
B．To explain the importance of finding alien life．
C．To introduce people's different views on alien life．
D．To show the hard evidence about the existence of alien life．