Final answer:
The correct answer is A. estaba.
Step-by-step explanation:
The correct answer is A. estaba. The verb estar is used in its imperfect form to describe a past action or state of being that was ongoing or continuous. In this sentence, the speaker is describing their mother's state of being tired during the morning. Since the action is in the past and ongoing, we use the imperfect form estaba.
Learn more about imperfect verb form in Spanish