Explicație:
1. We were very late, and the tour bus had already left before we arrived.
2. How long had Sam worked at the museum when they made him head of the Egypt Collection?
3. By the time we arrived at the museum, the archaeologist had finished her lecture.
4. Ivan was taking photos of the temple while Daniel was reading the museum's leaflet.
5. I had not visited Greece until I went there on a school trip last summer.
6. The archaeologists were excited because they had been looking for the ancient ruins for years.