Select the topic sentence.
[1] In the late seventeenth century a Turkish garrison was using the Parthenon for an ammunition storehouse. [2] During an attack by the Venetians, a bomb ignited the gunpowder, blowing up the center section. [3] Since then the building has been a glorious ruin. [4] Were it not for this relatively recent incident, the Parthenon would be standing intact today.