Final answer:
In Stage III of the demographic transition, both birth and death rates are relatively low, leading to a decrease in population growth rate. This stage follows the significant decline in the death rate and precedes the stage where both rates stabilize at a low level.
Step-by-step explanation:
In Stage III of the demographic transition, the correct answer is (a) the birth rate and the death rate are relatively low. During this stage, while the death rate has already declined due to improvements in healthcare, sanitation, and nutrition, the birth rate begins to fall due to changes in societal norms and increased access to family planning. This leads to a decrease in the population growth rate.
Looking at the demographic transition as a whole, in the earlier Stage I, both birth and death rates are high. As a country moves into Stage II, the death rate begins to fall due to various improvements, while the birth rate remains high. It's only later, in Stage III, that the birth rate starts falling, leading to slower population growth. Moreover, in Stage IV, both birth and death rates come to a low equilibrium, stabilizing the population.
Each stage of the demographic transition reflects the advancement and industrialization of a society, changing from a pre-industrial to an urban, post-industrial society with different social and economic characteristics at each stage.