Answer:
The correct answer is sabía.
Step-by-step explanation:
In this case we find a verb conjugated in the pretérito imperfecto tense verb.
This verb tense is used to describe an action in the past, to relate routines from the past, or to relate actions from the past that last over time.
Next I will write how to conjugate regular verbs in imperfect preterite of Spanish, depending on the verb ending:
AMAR TEMER PARTIR
Yo amaba Yo temía Yo partía
Tú amabas Tú temías Tú partías
Él/ella amaba Él/ella temía Él/ella partía
Nos. amábamos Nosotros/as temíamos Nosotros/as partíamos
Vosotros amabais Vosotros/as temíais Vosotros/as partíais
Ellos/as amaban Ellos/as temían Ellos/as partían