I wrote "It took seven years" and it was accepted as well.
How can it be "we have needed" when the verb is "sono" not "siamo?" This is a strange construction.
It's passive. the most natural form in Italian would be "ci sono voluti sette anni", but if you want to put emphasis on the fact that it needed SEVEN years, you can say "Sette anni ci sono voluti". A heavy construction can mean heavy feelings. ;)
Similar re-arranging can be seen in English, for example "Seven years it's taken to put up those flats!".
why is passive voice in this section?
the passive is very common in Italian
Fair enough, but that sounds like a good reason to put a whole section on the passive voice. This is the first section on a tense other than present; there's enough to be grappling with as it is!
I agree that it does add confusion in this section
Ok. So how does it work? ci + conjugated verb = have done?
ci vuole means it takes/wants eg ci vuole molto tempo,
however, if it is a "passive voice", i suppose the answer should be "seven years are needed" instead of "seven years were needed", because sono is the "present tense"