What are the primary statistics used to study population change, and what is the purpose of each?

The primary statistics that are used to study population change are that of the number of births, number of deaths, number of migrants, and number of people in each age group.

Explanation:

The number of births exhibit information about the natural biological increase in the population, the number of deaths shows the decrease in the population due to natural and accidental deaths, an increase or a decrease in the number of migrants helps in determining the demographic factors responsible for the increase or decrease in the population, and the number of people in each age group tells about the distribution of population over different age groups. There are four primary statistics that are used to study population change in any given area. On the basis of these statistics, the population and its distribution are determined. These statistics help in the formation of policies targeted towards specific populations and also helps in managing resources in a better manner.

The sun's parallax would be 180 degrees, greater than which you can't get.  so a. would be your anwser