Isn't (D) ambiguous?
Cathedrals were as much community centers as purely religious edifices could be:
1) Cathedrals were as much community centers as purely religious edifices were,
2) Cathedrals were as much community centers as they were purely religious edifices
Cathedrals were as much community centers as purely religious edifices could be:
1) Cathedrals were as much community centers as purely religious edifices were,
2) Cathedrals were as much community centers as they were purely religious edifices
