Final answer:
The correct answer is C. 'Ser' is used, because the sentence describes origin.
Step-by-step explanation:
The answer is C. 'Ser' is used in the sentence 'I am from the United Kingdom' because it describes the person's origin.
In Spanish, the verb 'ser' is used to describe permanent characteristics like nationality and origin.
For example, if you were to say 'Soy de España' (I am from Spain), you would use the verb 'ser' to indicate your origin.
Learn more about Choice of verb in a sentence based on context