If a country's death rate falls rapidly while its birth rate remains high for several years, what is the initial population response?

Correct answer: Acceleration of natural increase

Natural increase depends on the difference between births and deaths. If the death rate falls rapidly while the birth rate remains high, many births continue but fewer deaths occur. The gap between births and deaths therefore becomes wider, causing the population to grow more quickly at first. This is a common early pattern in demographic transition when improvements in sanitation, nutrition, or health reduce deaths before families substantially reduce births.

Option A is correct because it describes acceleration of natural increase. Immediate population decline would require deaths to exceed births, while zero growth would require them to be equal. The end of migration does not follow from the information, since migration is a separate component of population change. The question asks for the initial response, so later effects such as falling birth rates or changing age structure should not replace the direct result of fewer deaths and continued high births.