Hi, Mohamed, and welcome to the G.E,
Which is is correct?
By the time the firefighters arrived, the building ........
a) had burnt
b) had been burnt
I choose a, what about 'b'?
Thanks in advance
I see that both 'a' and 'b' are possible and that it is more natural to use 'burn down' here. 'Burn' is one of the ergative verbs, which means that it can be used transitively or intransitively. You can say:
1. By the time the firefighters arrived, the building had been / was burnt down by 'sb'. (It is a crime whether that person did it deliberately or accidentally).
2. By the time the firefighters arrived, the building had burnt / burnt down. (There is no crime here).