was studying or had been studying

[fadysandy]

I found this question in grammar book. I have already studied 'Past perfect continuous tense' and 'Past continuous tense' , but this sentence confused me.
Yesterday I was studying/ had been studying with my friends when my family had an emergency and I had to go home.
In my opinion, the second answer is correct. Am I OK?:roll:
Best regards.

 

[5jj]

They are both possible.

 

[tzfujimino]

May I ask a question here?:-D

I understand both are possible, but would it not be better if 'yesterday' were followed by a comma?
"Yesterday I was [...]" is fine, but "Yesterday I had been [...]" (without a comma) looks somehow odd to me.

Thank you.

 

[MikeNewYork]

It is very common to use a comma after an adverb at the beginning of a sentence. I would use a comma after "yesterday" in both versions.