"I had arrived a few minutes before."
Translation:Yo había llegado unos minutos antes.
"habia llegado unos minutos antes" was marked wrong, because I left out "yo".
Hi Frank, I am confused by this also, sometimes it is yo había, and sometimes me había, how can I know when to use which?
Hi Shirl, You have to use 'yo' because 'habia llegado' could mean 'I had arrived or he/she had arrived. When you use 'yo' it means 'I had arrived'. I would explain the difference between 'yo' and 'me' this way. 'Yo' is the subject pronoun ie I want = yo quiero, or I ran = yo corri. 'Me' pronounced 'may' is the the indirect object pronoun ie he called (to) me = el me llamo. In English it comes after the verb, in Spanish it comes before the verb. Hopefully this explains it, I am not a teacher but have been studying Spanish for a few years now but don't usually explain things very well.
This goes against the rule I always hear that "we already know about whom we are speaking". Other sources agree that "yo" is unnecessary.
Agree, yo is not required to be correct. It might be required to be clear, but not correct.
Yes, the standard accepted answer other places is not accepted here at random.
Why is this imperfect (había llegado) rather than preterite (hube llegado)? This event appears to have occurred at a very specific time.
Because había llegado is not Preterito Imperfecto (Imperfect) and hube llegado is not Preterito Indefenido (Simple past). had arrived is Past perfect which translates into Pluscuamperfecto => había llegado. Of course, there is a Preterito anterior => hube llegado, but it's almost never used in Spanish and really difficult to explain in a short comment.