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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

The population of the world has increased more in modern times than in all other ages of history combined. World population totaled about 500 million in 1650. It doubled in the period from 1650-1850. Today the population is more than five billion. Estimates based on research by the United Nations indicate that it will more than double in the twenty-five years between 1915 and the year 2000, reaching seven billion by the turn of the century.

No one knows the limits of population that the earth can support. Thomas Malthus, an English economist, developed a theory that became widely accepted in the nineteenth century. He suggested that because world population tended to “increase” more rapidly than the food supply, a continual strain was exerted upon available resources. Malthus cited wars, famines, epidemics, and other disasters as the usual limitations of population growth.

With recent advances in science and technology, including improved agriculture methods and great strides in medicine, some of the limiting factors in population growth have been lessened, with obvious results. International organizations have put forward several recommendations to alleviate the problem of overpopulation, including an increase in food production, general economic development in target areas, and a decrease in birth rates. Most experts agree that it will be necessary to combine all three recommendations in an effort to effect a lasting solution.

21. The title below that best expresses the ideas in this passage is ________.
A. Thomas Malthus's Theory
B. A Brief History of Population and Overpopulation
C. The United Nations' Estimate
D. Limiting Factors in Population Growth

22. The pronoun “it” in the first paragraph refers to ________.
A. the United Nations
B. century
C. research
D. population

23. According to this passage, why has overpopulation been caused?
A. improved technology
B. scarcity
C. disasters
D. population

24. The word “increase” in paragraph 2 is closest in meaning to ________.
A. precaution
B. decline
C. research
D. famines

25. Which of the following was NOT mentioned as the usual limitations of population growth?
A. Agricultural methods
B. Wars
C. Disasters
D. Famines
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