Final answer:
The correct term for a person from the northern region of a country is 'Northerner'. Thus, the option "A" is the correct answer.
Step-by-step explanation:
The term that best describes a person from the northern region of a country is A) Northerner. This designation is based on geographical location within a country, and it is used to differentiate between people from different parts of the same nation. The other terms listed—Southerner, Easterner, and Westerner—describe individuals from the southern, eastern, and western regions, respectively.