Population tends to grow at an exponential( 指数的)rate. This means that they progressively double. As an example of this type of growth rate take one penny and double every day for one month. After the first week, you would have only 64 cent, but after the fourth week you would have over a million dollars. This helps explain why the population has come on“all of a sudden”took from he beginning of human 1ife to the year 1830 for the population of the earth to reach one billion. That repents( 缓慢进行) a time span of at least two million years. Then it took from 1830 to 1930 for world population to reach 2 billion. The next billion was added by 1960 only thirty years and in 1975 world population reached 4 billion which is another billion people in only fifteen years. World population is increasing at a rate of 9, 000per hour, 220, 000 per day and 80 million per year. This is not only due to higher birth rate, but to lower death rate as well. The number of births has not declined at the same rate as the number of deaths. Some countries such as Columbia, Thailand, Morocco, Costa Rica and the Philippines are doubling their population about every twenty-one years with a growth rate of 3 percent a year or more. The United States is doubling its population about very eighty-seven years, with a rate of 0. 8 percent per year. Every time a population doubles, the country involved needs twice as much of everything, including hospitals, schools, resources, food and medicines to care for its people. It is easy to see that this is very difficult to achieve for the more rapidly growing countries. This passage chiefly discusses______________ A.the growth of world population. B.one type of the exponential rate. C.the population problem of more rapidly growing countries. D.the possible ways of dealing with the rapid population growth. According to the passage what helps to explain why the population problem has come on “all of a sudden” ?A.The penny that doubles itself every day for one month. B.The time span of at 1east two million years in human history. C.An illustration of the exponent growth rate given by the author. D.The large amount of money you would luckily make after the fourth week. It took_________ for the world to increase its population from 1 billion to 4 billion. A.100 years B.175 years C.1975 years D.over two million years Which of the following statements is NOT true?A.World population is increasing at a rate of 150 per minute. B.Lower death rate also contributes to world population growth. C.The population of Columbia has been doubling every year for 21 years. D.The United States is usually doubling its population on about every 87 years. When a population doubles, the country involved needs twice as much of everything including __.A.hospitals and medicines B.schools and students C.food and manpower resources D.all of the above