Read the passage and choose the best answer among A, B, C, D

The population of the world has increased more in the 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 about seven billion. Estimates based on research by the United Nations indicate that it will increase to over 10 billion by the turn of the century.

With recent advances in science and technology, including improved agricultural 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.