Step 1:
The year of great divide refers to an important turning point in India's population growth history.
Step 2:
Before 1921, India's population growth was irregular due to:
• Famines
• Epidemics
• High mortality rate
Step 3:
After 1921, population started increasing continuously due to improved health and living conditions.
Thus, 1921 became the dividing point.
Step 4:
Hence, the correct answer is:
\[
\boxed{\text{(2) 1921}}
\]