The answer would be: b. dio (since it's in third person).
Good luck!
Piscina: Ir al cine is the answer
El sábado pasado caminé hasta la casa de mi abuelita porque no encontré un taxi.
The speaker is saying this whole thing happened last Sunday, meaning the verb should be in past tense. Also, the speaker says they didn't find a taxi. Someone who didn't find a taxi is likely to walk to their destination instead. So, we can assume the blank is caminé.
