<span> Answer: demography </span>
<span>We can identify which of the scientific studies describe population thru their definitions.</span>
Gerontology is particular with old<span> age, its process and the problems are encountered by old people.</span>
Psychology studies the feeling<span>, behavior, and mind of people, including all phenomena.</span>
Demography<span> shows the structure of human population, how it changes, based on the statistics of births, deaths, income, or occurrence of disease, the composition of a particular human population.</span>
Geography is <span>understanding of the Earth. And it's complexities. </span>
<span>Correct answer then is demography.</span>