Below is a text with blanks. Click on each blank, a list of choices will appear. Select the appropriate answer choice for each blank.
下面的文本有一些空格。点击每个空格会出现一组选项，请为每个空格选出最合适的答案。
Populations can change through three processes: fertility, mortality and migration. Fertility involves the number of children that women have and differs from fecundity (a woman's childbearing potential). Mortality the causes, consequences and measurement of processes affecting death in a population. Demographers most commonly study mortality using the Life Table, a statistical which provides information about the mortality conditions (most notably the life expectancy) in the population. Migration refers to the movement of persons from an origin place to a destination place across some pre-defined political boundary. Migration researchers do not designate movements as migrations' they are somewhat permanent. Thus demographers do not consider tourists and travelers to be migrating. While demographers who study migration typically do so through census data on place of , indirect sources of data including tax forms and labor force surveys.
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