人类的新方式，但是地球上拥挤的状况也使得人们去寻找更开阔的空间。由此可知，人口膨胀最大的问题是空间的问题。故选D项。

　　2．Carl Sagan believes that Venus might be a living place because________.

　　A．the days on Venus are long enough

　　B．it might be possible to change its atmosphere

　　C．there is a good supply of water on Venus

　　D．its atmosphere is the same as the earth's

　　解析：选B　细节理解题。根据第二段第一句"... it will be possible to change the atmosphere of Venus and so create a new world almost as large as the earth itself."可知，金星有可能改变它的大气继而成为适宜人类生存的地方。故选B项。

　　3．Algae are plants that can________.

　　A．live in very hot temperature

　　B．live in very cold temperature

　　C．produce oxygen

　　D．all of the above

　　解析：选D　细节理解题。根据第三段第一句可知，海藻有机体可以在极热和极冷的温度下生存，同时还能产生氧气。故选D项。

　　4．Man can land on Venus only when________.

　　A．it rains there

　　B．there is oxygen

　　C．the atmosphere becomes cooler

　　D．the algae have done their work

　　解析：选A　推理判断题。在文章最后一段中提到，在人类踏足金星之前需要氧气去制造雨水，然后又提到雨水最后会降落到金星上使得气温下降，这样人类就可以居住了。由此可以推测A项正确。

　　B

　　Welcome to our homepage!

　　We've teamed up with two travel agencies to give members of our club the chance to win a holiday to the South of France or one to the Maldives.

The winner and our three guests will enjoy a seven­night getaway (短假) at the Villa Le Priotlet - a centuries old stone villa (别墅) set on the banks of the Dordogne River. This property