Imperfect Vs Preterite

Question

I notice that in the test question "iba" was used, but in the example here the preterite "fueron" is used. How do we know which to use and when?

Answer

Hola HarkonnenThe use of the preterite (fueron) or the imperfect (iban) in this structure is the same as in the general difference between the preterite and the imperfect as such. The preterite always conveys somehow that the action is completed while the imperfect doesn't. Using them as part of this structure which expresses "progression" makes it more difficult to see that "completion of the action" but when the speaker says  "fueron terminando las preguntas" the action is seen as a progression, however inside that progression they see a completion, as if they were finishing the questions bit by bit and each time that action was finished, continued and finished, continued and finished, etc. With "iban terminando", this wouldn't be perceived as such.Saludos

Answer

Tuve la misma pregunta. La idea de progresión me parece más adecuada para el imperfecto que para el pretérito, por lo que el uso de fueron me pareció ilógico. Creo que sería útil explicar este matiz en la lección.