Final answer:
The sentence 'El tiempo estaba lloviendo mucho' uses the Imperfect tense.
Step-by-step explanation:
The sentence that uses the Imperfect tense is 'El tiempo estaba lloviendo mucho.'
In Spanish, the Imperfect tense is used to describe past actions, states, or habits that were ongoing or repeated in the past. It is often used to describe the weather, time, age, emotions, and physical or mental states.
In the given sentence, 'El tiempo' (the weather) is the subject and 'estaba lloviendo mucho' (was raining a lot) is the verb phrase in the Imperfect tense.
Learn more about Imperfect tense in Spanish