The decade 1911-1921 is known as the "Great Divide" in India's demographic history because it was the only decade when India experienced a negative population growth rate (-0.31%). This was primarily due to the devastating influenza pandemic of 1918, which caused high mortality across the country. While undivided Bengal Presidency saw a slight positive growth overall during this period (approx. 1.89%), certain districts within Bengal experienced significant population decline due to the pandemic's impact. The option -1.77% represents a plausible negative growth rate for the territory corresponding to West Bengal, reflecting the severe impact of the pandemic in that region, even if the broader province showed a small increase.