Final answer:
The sentence 'Rosa vivia en Londres' is in the imperfect form, used to describe ongoing or repeated actions in the past.
Step-by-step explanation:
The given sentence 'Rosa vivia en Londres' is in the imperfect form in Spanish. The imperfect tense is used to describe ongoing or repeated actions in the past. It is formed by adding the appropriate endings to the stem of the verb. In this case, the verb 'vivir' (to live) is conjugated in the imperfect form as 'vivia' to indicate that Rosa used to live in London.
Learn more about Imperfect tense in Spanish