What countries were the most heavily populated countries in the 20th century?

When it comes to population, numbers have always tended to be highest in Asia. Currently, Asia holds around 4.4 billion inhabitants, just over 60% of the world's population. Within it, China and India clearly stand out as the countries with the largest populations, totaling more than 2.6 billion people combined.

1 China
2 India
3 United States
Hope it helps

Aor b but i'm going with b