What change in demographics was observed in developed countries in the twenty-first century? A. falling birth rates but shorter life expectancy B. falling birth rates and longer life expectancy C. sharp rises in birth rates and shorter life expectancy D. rising birth rates and longer life expectancy

The change in demographics observed in developed countries in the twenty-first century was falling birth rates and longer life expectancy. Option B is correct.

The world population is growing further slowly than it used to since birth rates have been reduced in numerous countries. At the same time, life expectancies have increased considerably.

In more than 80 countries, the birth rate is below the level of 2.1 children per woman.