Aloyalty to one area or section of a country instead of the country as a whole is defined as a. secede b. sectionalism c. popular soverignty d. nullify : )

The answer would be B, sectionalism. Loyalty to the country as a whole would be nationalism. 
A good way to remember the difference is that loyalty to the national  government is nationalism, while loyalty to a section of the country is sectionalism.