Present Perfect vs Past Perfect:
1 builda) Look at this concert hall! They it recently.b) They most of the cathedrals before others came to their land.2 be marrieda) By the time their first baby was born, my friends for 5 years already.b) I (never).3 knowa) Last week I was introduced to George. I him before.b) Michael is a cool guy. I him for ages.4 worka) When my father was promoted to a senior position, he at the factory for 20 years.b) I with her since my first day in this company.5 leavea) Mary (just) the office.b) By the time the bell rang, everyone (already).6 Mary and John are such a lovely couple. I always them. (like)7 My aunt is in poor health. She in hospital since Monday. (be)8 Parents to their children before the party, so they behaved quite well. (talk)9 I didn't introduce Katie and Ann to each other, they already before. (meet)10 I am going to the library to return this book. I it already. (read)