Concept:India’s population growth is divided into four phases based on changes in birth and death rates. Phase III (1951–1981) experienced a population explosion because the death rate fell sharply while the fertility rate stayed high.
Explanation:Step 1: Phase I (1901–1921) had high mortality due to famines and epidemics, so growth was stagnant – not an explosion. Hence option C is wrong.
Step 2: Phase II (1921–1951) saw a gradual decline in death rate but birth rate remained high, leading to moderate growth – not “high mortality” as given in option D.
Step 3: Phase III (1951–1981) witnessed a steep fall in death rate due to better healthcare, public health measures, and the Green Revolution. However, the birth rate remained high, creating a rapid population increase – a “population explosion”.
Step 4: Phase IV (post-1981) experienced declining fertility rates because of family planning and improved socio-economic conditions, not a sudden increase in fertility. So option A is incorrect.
Thus, only option B correctly matches the phase with its characteristic.
Answer:B. Phase III (1951-1981) – Population explosion caused by falling death rate and high fertility.