We ... at the airport at six o'clock
b had arrived
c were arriving
All my English teachers have told me that I should not mention a specific time when I use the past perfect, however, yesterday my answer was qualified as incorrect. It said: We ... at the airport at six o'clock. I replied that it was a simple past sentence, being the verb "arrived". My English teacher marked me as wrong, and told me it was past perfect. Is my English teacher correct? Can you mention a specific time in the past perfect? The closest thing I found in my book was a sentence ("We had finished the tour by two o'clock") that used the perfect past and mentioned an approximate time, since it uses the word "by", which is not an exact time.