Choose the correct form of the 3rd conditional: 1.if the titanic (didn't hit / hadn't hit) an iceberg, it (wouldn't have sunk / doesn't sink) . 2.if the aztecs (had defeated / defeated) cortes' soldiers, the spanish (mightn't conquered / mightn't have conquered) mexico. 3.what (happened /would have happened) if columbus (thought /had thought) the world was flat? 4.if the tsar's soldiers (hadn't shot / wouldn't shoot) demonstrating workers in 1905, there (mightn't been / mightn't have been) a revolution in russia. 5.john kennedy (couldn't be assassinated / mightn't have been assassinated ) in 1963 if he (hadn't been travelling / hadn't travelling) in an open-top car.