Final answer:
Option B is correct: The 10 nations predicted to have the largest populations by 2050 are all developing countries, with India expected to be the most populous, surpassing China around 2025.
Step-by-step explanation:
An examination of the world's population and predictions for future populations, based on the information provided, suggests that option B is the correct answer. By the year 2050, it is expected that the 10 nations with the largest populations will all be developing countries. Evidence supporting this includes the U.S. Census Bureau forecasting that India will surpass China as the most populous nation around 2025, and Nigeria's population is predicted to increase significantly.
Additionally, it is noted that although birth rates and family sizes are declining in most developing countries, due to urbanization, the overall population will continue to grow substantially because of the existing large base population. Lastly, regarding option E, India is projected to have the largest population by 2050, not China, which contradicts the statement in the question.