Estuve...?

[Rusty]

The reason is that an action in progress was interrupted. The progressive tenses are used to convey 'being in the very act of doing something'.

[AngelicaDeAlquezar]

Originally Posted by Elaina

Why can't it be..........Estudiaba cuando entró el profesor.... (it's an incomplete sentence but.....it sounds right to me. Would I be breaking a grammar rule?

Thanks!

It's a matter of style to avoid it, but it's a right sentence, and to my mind, gramatically correct as well.

[chileno]

Originally Posted by irmamar

En España no se usa "estar retrasado" para decir que llegas tarde. Una persona retrasada es una persona que no se ha desarrollado bien.

El autobús va retrasado o va con retraso.
Yo llego tarde, voy con retraso o me retraso.

¿Y demorado? No, no es el color...

[CrOtALiTo]

I believe that the sentence correctly written is Estube hasta tarde, I feel that the build of the verb wasn't the more correct without this word hasta, this word complete the sentence and sound well.