The correct answer is: c) Rapid urbanization.
Nagaland’s population has increased rapidly since the 1951 Census, with the urban population growing at a much faster rate than the rural population. This has led to a number of challenges, including increased pressure on infrastructure, environmental degradation, and social unrest.
The following are brief explanations of each option:
a) A decrease in population density: This is not a significant change in Nagaland’s population since the 1951 Census. The population density of Nagaland has increased from 125 people per square kilometer in 1951 to 240 people per square kilometer in 2011.
b) A decline in the sex ratio: This is not a significant change in Nagaland’s population since the 1951 Census. The sex ratio of Nagaland has remained relatively stable at around 950 females per 1000 males.
d) A decrease in literacy rates: This is not a significant change in Nagaland’s population since the 1951 Census. The literacy rate of Nagaland has increased from 39% in 1951 to 79% in 2011.