Concept:Population growth is determined by birth rate, death rate, and net migration.
Explanation:Birth rate measures live births per
1,000 persons in a year.
When birth rate rises, the number of births in the country increases beyond deaths.
That adds more people to the population, so population size rises.
For example, if a country records more births than deaths each year, it experiences natural increase.
Higher death rate reduces population because more people die.
Poor medical facilities also lead to higher death rate and lower life expectancy.
Decrease in birth rate lowers the number of births, slowing population increase.
Therefore, of all the options, only an increase in birth rate can increase a country's population.
Answer:A. increase in birth rate.