Abrías;durmió
“Mientras” is a present word so it’s happening now, the rest of the sentence should be present too, so abrías and durmió
1. La estación de ferrocarriles/tren
2. Subir
3. Bajar
4. La ventanilla
5. El anden
My explanation is that tren is train for Spanish and subir is get in, Bajar is get off , la ventanilla is window and el anden is where you wait for the train
La respuesta correcta es
C)podíamos
Large and Pretty! Hope I helped Amigo!