The correct answer is option 1, 1921-1931. This period is referred to as "A Great Leap Forward" in the history of Indian population. During this time, India experienced a significant increase in population growth compared to previous decades. The growth rate during this period was around 1.3% per year, which was the highest at that time. This period also marked a shift from a stagnant or slow-growing population to a more rapid population growth, driven by improvements in healthcare, sanitation, and living conditions. This growth had significant implications for India`s socio-economic development and resource management. It is important to note that while this period was indeed a significant leap forward in population growth, the term "A Great Leap Forward" is not associated with the economic and social transformation in China during the 1950s.