It was back in the 14th century that the Great Wall of China ___ (undergo) reconstruction.
underwent
The lead actor ____ (hold) everyone's attention with his final, impassioned speech when, to my horror, my mobile ____ (go off).
was holding - went off
The area now known as Pompeii ____ (inhabit) since the Bronze Age. But in 79 AD, Mount Vesuvius ___ (erupt) and ____ (wipe out) all signs of life.
had been inhabited - erupted - wiped out