3.
Choose the answer which best completes the sentence in suitable and accurate English.
'They ... ... asbestos into so many schools and hospitals, if they'd known back then how dangerous it ... ... .'
... shouldn't build ... / ... was ...
... would never have built ... / ... is ...
... would never have built ... / ... was ...
... shouldn't have built ... / ... was ...
Answer 2 is more a North American usage; Answer 3 is simply, though understandably, wrong (with its Imperfect / continuous form suggesting that such disciplinary meetings were indeed a fairly regular occurrence); Answer 4 is just about possible, but sounds very mannered and old-fashioned ~ no modern employee would take such a usage as seriously as the speaker would have meant or liked!