The following sentences contain blanks. Use the drop-down menus to complete each blank correctly. Many people throughout the world are free to travel across and live within the borders of a country. Only [Dropdown 1] , however, can establish official borders. These borders are often established through [Dropdown 2] , or formal negotiated agreements. Sometimes these agreements are broken when one country ignores the established borders and claims land beyond its boundaries. This type of aggressive state behavior is called [Dropdown 3] .