Final answer:
A country in stage 2 of the demographic transition model experiences a high natural increase rate due to high birth rates and falling death rates, leading to rapid population growth.
Step-by-step explanation:
A country would experience a high natural increase rate in stage 2 of the demographic transition model (DTM) primarily due to high birth rates and falling death rates. At this stage, the impact of improved healthcare and nutrition extends life expectancy, causing death rates to decline.
However, birth rates remain high because of cultural norms and the lack of widespread access to birth control, leading to rapid population growth. Populations in stage 2 countries often exhibit a large base in their population pyramid, indicating a high number of births relative to the rest of the population.