The preterite "yo" form of the verb "estar" is "estuve."
Explanation:
1. "Estar" is an irregular verb in Spanish.
2. In the preterite tense (simple past), the conjugation for the "yo" form (I) of "estar" is "estuve."
3. For example:
- "Yo estuve en la fiesta ayer." (I was at the party yesterday.)
Therefore, the correct answer is:
c. estuve
