The number of people entering a population through 'big' or immigration' being equal to the number of people leaving it via 'emigration' or 'death' is called:

Correct option is C

Correct Answer: (c) Zero population growth

Explanation:
Zero population growth (ZPG) occurs when the number of people entering a population (through births or immigration) equals the number of people leaving the population (through deaths or emigration). In this state, the population size remains stable, neither increasing nor decreasing over time.

This concept is significant in demographic studies and environmental sustainability, as it represents a balanced scenario where resources and population are in equilibrium.

Knowledge Booster:
● Zero population growth is often associated with developed countries where birth and death rates are low and balanced.
● Achieving ZPG is one of the goals of population stabilization programs.
● Countries with ZPG often face challenges such as an aging population and labor shortages.
● High immigration rates can disrupt ZPG, even if the natural birth-death balance is achieved.
● This concept is essential for sustainable resource management and environmental conservation.

Additional Information:
● Positive population growth (Option a): Occurs when births and immigration exceed deaths and emigration, leading to an increasing population.
● Rapid population growth (Option b): A high growth rate due to significantly higher birth rates compared to death rates, often seen in developing countries.
● Negative population growth (Option d): Occurs when deaths and emigration exceed births and immigration, causing the population to decline.