Many of the world’s pollution problems have been caused by the crowding of large groups of people into the cities. Supply for the needs of the people leads to further   1   by industry. If the rapid increase of world 2   continues at the present rate, there may be much greater 3   to human beings. Some scientists 4   of the increase in numbers of people as “population pollution（人口公害）”.
About 2, 000 years ago, the world population was about 250 million. It  5  a billion in 1850. By 1930 the population was two billion. It is now six billion. It is  6  to double by the year 2020. If the population  7   to grow at the same rate, there will be 25 billion people in the 8    a hundred years from now.
Man has been 9   the earth’s resources more and more 10   over the past years. Some of them are almost gone. Now many people believe that man’s 11   problem is how to control the 12   of the population. The material supplies in the world will be far from enough to  13  the human population if the present rate of increase continues. There is already over-crowding（过分拥挤）in many cities and  14  in some countries. Many people believe that human survival（生存） in the future  15  on the answer to the question.

A．progress B．pollution C．education D．production

A．agriculture B．industry C．environment D．population

A．danger B．harm C．benefit D．hardship

A．dream B．approve C．rid D．speak

A．got B．took C．brought D．reached

A．suggested B．hoped C．expected D．said

A．continues B．fails C．tries D．means

A．world B．country C．star D．end

A．discovering B．using C．digging D．destroying

A．seriously B．dangerously C．rapidly D．steadily

A．greatest B．easiest C．lightest D．simplest

A．existence B．start C．growth D．birth

A．increase B．decrease C．report D．support

A．discussion B．starvation C．construction D．argument

A．depends B．agrees C．saves D．passes