i. Year 1921 was known as demographic divide because there was decrease is decrease there is decrease in death rate and increase in birth rate. The change  started after the passing of the influenza pandemic.
ii. During the 30 years of period 1951 - 81 due to decrease in death rate the population growth rate led to the population explosion. In this period India's population increased from 251 to 361 million with growth of 47.3 percent. 

i. In under developed countries, rapid growth of population diminishes the availability of capital per head which reduces the productivity of its labour force.

ii. A rapidly growing population increases the requirements of demographic investment which at the same time reduces the capacity of the people to save.

iii. A rapidly growing population leads to a progressive decline in the availability of capital per worker. This further leads to lower productivity and diminishing returns.

iv. The rapidly rising population makes it almost impossible for economically backward countries to solve their problem of unemployment.

i. Preference of male child over female.

ii. The role of education has a great influence on the sex ratio scenario of India. Child marriages are a common part of the Indian society.

iii. Majority of the places in India follow the patriarchal system.In India, males are considered to be the only bread earners.

iv. Due to female foeticide, the sex ratio declines terribly. Maternal mortality also contributes to the declining sex ratio as most of the women die during the childbirth due to improper care and less facilities.

i. Birth rates are higher in the rural areas.
ii. Large number of adults migrate from rural areas to urban areas in search of Job and better facilities of life.