Verbena : Where did you go last Saturday?
Egi : I went to my mother's doctoral graduation ceremony.
Verbena : Ah, I remember that she took a doctoral program, right?
Egi : Yes. She has studied for doctoral program since 2019.
Verbena : By the way, what did she study?
Egi : she — civil engineering.
studied
Discussion:
The above sentences use simple past tense. In the simple past tense, we use past verbs (V2) such as studied. Use studied because direct Object/Complement.