The population of a country will decrease if

The population of a country will decrease if the death rate exceeds the birth rate. This means that the number of people dying in a given period of time is higher than the number of babies being born. For example, if a country has a birth rate of 10 babies per 1000 people per year and a death rate of 15 people per 1000 per year, the population will decrease. This is because more people are dying than are being born. Immigration being equal to emigration means that there is no net migration, which does not directly impact the population growth rate. Rapid economic growth may lead to an increase in population due to factors such as increased job opportunities and improved living standards, but it is not a direct cause of population decrease. Therefore, the correct answer is option A, the death rate exceeding the birth rate, which will lead to a decrease in population.