The correct answer is: d) All of the above.
Nagaland has a high fertility rate, which means that women have an average of more than three children each. This is one of the highest fertility rates in the world. High fertility rates lead to population growth because more people are being born than are dying.
Nagaland also has a low mortality rate, which means that people are living longer. This is due to a number of factors, including improved healthcare and nutrition. Low mortality rates also lead to population growth because fewer people are dying than are being born.
In addition to high fertility rates and low mortality rates, Nagaland also has a high rate of immigration. This means that more people are moving into the state than are moving out. Immigration can also lead to population growth because it increases the number of people living in a state.
Therefore, all of the above factors contribute to population growth in Nagaland.