The geographic theories of burgess, hoyt, and von thunen us study how develop.

a.
human settlements
b.
languages
c.
migration patterns
d.
populations

C.

Migration is moving to another country to permanently or semi-permanently stay there. It is one of the main causes of population change. The basic principle is when you move from country A to country B, country A loses one citizen and country B gains one. Due to economic and political reasons, the rate of migration is increasing. On one hand, migration can help increase the human resources of countries lacking it. It can help balance population between countries. On another, mass migration can cause economic problems. Currently, Europe is facing major crisis in catering immigrants from Syria and other countries. 

This would be an open primary. a closed primary people can vote only prior to election day if the party if they are registered. independent voters can not participate. there is not a wide-open primary, but there is a semi-open primary.

The answer to the first one is barometer.