To complete this exercise, you have to select the sentence that has a regular verb in the imperfect tense.
The <u>Spanish imperfect tense</u> ("pretérito imperfecto" in Spanish) is used to talk about past habitual actions or to talk about what someone was doing but then got interrupted with something else.
"Vivir" is a regular verb. In the imperfect tense, all the verbs that end with "-ir" in the third person plural form are conjugated with "-ían", so the verb is "vivían".