Final answer:
The Imperfect tense is used to talk about past actions that were ongoing or habitual. Option b. Ella estaba sorprendida. uses the Imperfect tense to describe a state of being in the past.
Step-by-step explanation:
The Imperfect tense is used to talk about past actions that were ongoing or habitual. It is formed by adding specific endings to the stem of the verb. Option b. Ella estaba sorprendida. uses the Imperfect tense because this sentence describes a state of being in the past. The verb 'estar' is conjugated in the Imperfect tense as 'estaba' to indicate that she was surprised at that time. This tense is commonly used to describe ongoing actions, conditions, or states in the past.
Learn more about Spanish grammar