The correct answer is B. Region
Step-by-step explanation
A region is a word that refers to a portion of territory determined by common characteristics or special circumstances, such as the climate, the topography, or the form of government. Additionally, the region is a territorial division, defined by geographical, historical, and social issues, which has several subdivisions, such as departments, provinces, cities, and others. According to the above, the theme of Geography used to study an area with similar parts but different from other areas is B. Region.