To determine which statement best explains how the Monroe Doctrine encouraged the territorial changes shown in Source 2, we can analyze the options based on the provided information:
A. It promoted hostile relations between Great Britain and the United States. - This doesn't directly relate to territorial changes.
B. It allowed the United States to gain Texas from Mexico. - While this is a historical event, it is not primarily a result of the Monroe Doctrine.
C. It discouraged European powers from further colonizing the Western Hemisphere. - This aligns with the core message of the Monroe Doctrine, which aimed to prevent European intervention or colonization in the Americas, thus potentially facilitating territorial expansion by the U.S.
D. It called for the forceful seizure of Florida from Spanish control. - While the U.S. did acquire Florida, the Monroe Doctrine itself did not specifically call for this action.
Given this analysis, the best answer would be:
C. It discouraged European powers from further colonizing the Western Hemisphere.