Answer:
a. increasing birth rate with a greater number of young organisms
Explanation:
When the population growth is increasing in an area there is an increasing birth rate and the age structure begins to young.
Population growth is the increasing trend in population parameters that ensures that more organisms are produced.
The birth rate is the chief factor that populates an area.
When birth rate increases, new and younger organisms are produced and this tips the population towards a very young age.
An ageing population is one where the birth rate is quite low.
