Which age pyramid has the largest base of pre-reproductive population ?

By looking at all the age population pyramids, this would be my best guess. Every territory is different with various populations, however, to the best of my knowledge, it would be the expansive pyramid.

Expansive population pyramids are used to describe populations that are young and growing. They are often characterized by their typical ‘pyramid’ shape, which has a broad base and narrow top. Expansive population pyramids show a larger percentage of the population in the younger age cohorts, usually with each age cohort smaller in size than the one below it. These types of populations are typically representative of developing nations, whose populations often have high fertility rates and lower than average life expectancies.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.