68．From the passage we know that .
A．US President George W. Bush visited China on Monday
B．Chinese Foreign Minister Li Zhao xing visited the USA on Monday
C．Chinese President Hu Jintao visited US President George W. Bush on Monday .
D．US President George W. Bush will go to China soon
69．George W. Bush said that the USA .
A．sticks to the One-China policy
B．abides by the three joint communiques between the two nations
C．is against the "independence of Taiwan"
D．all the above
70．According to Li Zhaoxing , China and the USA cooperated in the areas of .
A．economy and education B．education and military affairs
C．economy and trade D．trade and military affairs
71．What is the most important and sensitive issue in the Sino-Us relationship ?
A．The Taiwan issue .
B．The Iran issue .
C．The nuclear issue of the Democratic People's Republic of Korea .
D．Both the Taiwan issue and the nuclear issue of the Democratic People's Republic of Korea .
(E)
For more than twenty years scientists have been searching for signs of life on other planets . Most of these searches have been done over the radio. The hope is that someone in outer space may be trying to get in touch with us . Scientists also have sent radio and television messages on spaceships traveling through space , on the chance that someone may be receptive to such messages .
Scientists are using powerful radio telescopes to listen to signals from about 1,000 stars , all within 100 light years of Earth . In addition , they scan the entire sky to "listen" for radio messages from more distant stars .Using a computer , they will be able to monitor more than eight channels at a time . Scientists are looking for any signal that stands out from the background noise .
Of the 200 billion stars in the Milky Way Galaxy (银河星系), scientists find that five percent are like our sun . Perhaps half of them have a planet like Earth . Such a planet would be a reasonable distance from the star for temperatures to be right for the evolution (进化) of life . Based on the inhabitable (that can be lived in ) planets in our Galaxy most scientists agree that chances are likely that one or more of these planets support some life .
However , many scientists wonder whether intelligent life exists on other planets . Some believe that twenty years of searching without any intelligible messages shows that no one is out there . They say that the evolution of intelligence comparable to ours is unlikely .
Other scientists believe that our search hasn't been long enough to rule out the possibility that intelligent life exists in our Galaxy . Although our sun family is only about five billion years old , our Galaxy is about 20 billion years old . In that case , some scientists think that it is likely that civilization much more advanced than ours have developed . Perhaps these civilizations send us no signals ; perhaps we have not recognized the signals they have sent us . If we hope to find intelligent life , these scientists believe that we have to keep looking .